| 2003-03-31 | vs PIT | 1 | L 1-10 | 0-1 | 4 | 42,343 | Jimmy Haynes | Kris Benson | Kris Benson | Jimmy Haynes | | 1 | 10 | -9 |
| 2003-04-02 | vs PIT | 2 | L 4-7 | 0-2 | 5 | 22,878 | Ryan Dempster | Kip Wells | Salomon Torres | Josias Manzanillo | Mike Williams | 5 | 17 | -12 |
| 2003-04-03 | vs PIT | 3 | L 5-7 | 0-3 | 5 | 26,096 | Jimmy Anderson | Josh Fogg | Josh Fogg | Jimmy Anderson | Mike Williams | 10 | 24 | -14 |
| 2003-04-04 | vs CHN | 4 | W 10-9 | 1-3 | 5 | 29,048 | Danny Graves | Shawn Estes | Scott Williamson | Dave Veres | | 20 | 33 | -13 |
| 2003-04-05 | vs CHN | 5 | L 7-9 | 1-4 | 5 | 28,908 | Jimmy Haynes | Carlos Zambrano | Carlos Zambrano | Jimmy Haynes | Joe Borowski | 27 | 42 | -15 |
| 2003-04-06 | vs CHN | 6 | W 5-4 | 2-4 | 5 | 24,023 | Paul Wilson | Kerry Wood | Gabe White | Mark Guthrie | Scott Williamson | 32 | 46 | -14 |
| 2003-04-08 | @ HOU | 7 | W 2-1 | 3-4 | 5 | 18,594 | Ryan Dempster | Roy Oswalt | Ryan Dempster | Octavio Dotel | Scott Williamson | 34 | 47 | -13 |
| 2003-04-09 | @ HOU | 8 | L 3-4 | 3-5 | 5 | 20,794 | Jimmy Anderson | Wade Miller | Brad Lidge | Josias Manzanillo | Billy Wagner | 37 | 51 | -14 |
| 2003-04-10 | @ HOU | 9 | L 2-4 | 3-6 | 5 | 20,842 | Danny Graves | Jeriome Robertson | Jeriome Robertson | Danny Graves | Billy Wagner | 39 | 55 | -16 |
| 2003-04-11 | vs PHI | 10 | W 7-6 | 4-6 | 5 | 27,738 | Paul Wilson | Brett Myers | Scott Williamson | Jose Mesa | | 46 | 61 | -15 |
| 2003-04-12 | vs PHI | 11 | L 5-8 | 4-7 | 5 | 28,598 | Jimmy Haynes | Kevin Millwood | Kevin Millwood | Jimmy Haynes | | 51 | 69 | -18 |
| 2003-04-13 | vs PHI | 12 | L 1-13 | 4-8 | 5 | 24,535 | Ryan Dempster | Randy Wolf | Randy Wolf | Ryan Dempster | | 52 | 82 | -30 |
| 2003-04-14 | @ CHN | 13 | W 11-3 | 5-8 | 5 | 37,528 | Jimmy Anderson | Mark Prior | Jimmy Anderson | Mark Prior | John Riedling | 63 | 85 | -22 |
| 2003-04-15 | @ CHN | 14 | L 1-11 | 5-9 | 5 | 31,642 | Danny Graves | Shawn Estes | Shawn Estes | Danny Graves | | 64 | 96 | -32 |
| 2003-04-16 | @ CHN | 15 | L 4-10 | 5-10 | 5 | 27,388 | Paul Wilson | Carlos Zambrano | Carlos Zambrano | Paul Wilson | | 68 | 106 | -38 |
| 2003-04-17 | @ CHN | 16 | L 3-16 | 5-11 | 6 | 29,672 | Jimmy Haynes | Kerry Wood | Kerry Wood | Jimmy Haynes | Alan Benes | 71 | 122 | -51 |
| 2003-04-19 | @ MON | 17 | L 7-8 | 5-13 | 6 | 10,296 | Ryan Dempster | Zach Day | Luis Ayala | Scott Williamson | | 78 | 130 | -52 |
| 2003-04-19 | @ MON | 18 | L 5-9 | 5-13 | 6 | 13,109 | Jimmy Anderson | Javier Vazquez | Javier Vazquez | Jimmy Anderson | | 83 | 139 | -56 |
| 2003-04-20 | @ MON | 19 | W 7-5 | 6-13 | 6 | 11,619 | Danny Graves | Tony Armas | Scott Sullivan | Luis Ayala | Scott Williamson | 90 | 144 | -54 |
| 2003-04-22 | vs LAN | 20 | L 1-2 | 6-14 | 6 | 19,029 | Paul Wilson | Kazuhisa Ishii | Paul Shuey | Paul Wilson | Eric Gagne | 91 | 146 | -55 |
| 2003-04-23 | vs LAN | 21 | W 3-0 | 7-14 | 6 | 21,402 | Chris Reitsma | Darren Dreifort | Chris Reitsma | Darren Dreifort | Scott Williamson | 94 | 146 | -52 |
| 2003-04-24 | vs LAN | 22 | W 3-2 | 8-14 | 5 | 24,333 | Ryan Dempster | Kevin Brown | Felix Heredia | Guillermo Mota | | 97 | 148 | -51 |
| 2003-04-25 | vs SDN | 23 | L 3-7 | 8-15 | 6 | 22,453 | Jeff Austin | Jake Peavy | Jake Peavy | Jeff Austin | | 100 | 155 | -55 |
| 2003-04-26 | vs SDN | 24 | W 7-6 | 9-15 | 5 | 23,521 | Danny Graves | Clay Condrey | Felix Heredia | Jaret Wright | | 107 | 161 | -54 |
| 2003-04-27 | vs SDN | 25 | W 7-5 | 10-15 | 5 | 25,466 | Paul Wilson | Brian Lawrence | Paul Wilson | Brian Lawrence | Scott Williamson | 114 | 166 | -52 |
| 2003-04-29 | @ COL | 26 | L 5-10 | 10-16 | 5 | 26,206 | Chris Reitsma | Jason Jennings | Jason Jennings | Chris Reitsma | | 119 | 176 | -57 |
| 2003-04-30 | @ COL | 27 | W 13-11 | 11-16 | 5 | 26,436 | Ryan Dempster | Aaron Cook | Scott Sullivan | Dan Miceli | Scott Williamson | 132 | 187 | -55 |
| 2003-05-01 | @ COL | 28 | W 7-2 | 12-16 | 4 | 28,788 | Jeff Austin | Nelson Cruz | Jeff Austin | Nelson Cruz | | 139 | 189 | -50 |
| 2003-05-02 | @ SFN | 29 | W 5-1 | 13-16 | 4 | 35,486 | Danny Graves | Kurt Ainsworth | Danny Graves | Kurt Ainsworth | | 144 | 190 | -46 |
| 2003-05-03 | @ SFN | 30 | L 6-9 | 13-17 | 5 | 40,077 | Paul Wilson | Jesse Foppert | Jesse Foppert | Paul Wilson | Tim Worrell | 150 | 199 | -49 |
| 2003-05-04 | @ SFN | 31 | L 1-6 | 13-18 | 5 | 41,163 | Ryan Dempster | Kirk Rueter | Kirk Rueter | Ryan Dempster | | 151 | 205 | -54 |
| 2003-05-05 | vs SLN | 32 | W 5-4 | 14-18 | 5 | 20,145 | John Riedling | Woody Williams | Scott Williamson | Dustin Hermanson | | 156 | 209 | -53 |
| 2003-05-06 | vs SLN | 33 | W 6-5 | 15-18 | 4 | 25,917 | Jeff Austin | Brett Tomko | Chris Reitsma | Kiko Calero | | 162 | 214 | -52 |
| 2003-05-07 | vs SLN | 34 | W 4-2 | 16-18 | 4 | 20,849 | Danny Graves | Jason Simontacchi | Danny Graves | Jason Simontacchi | Scott Williamson | 166 | 216 | -50 |
| 2003-05-08 | vs SLN | 35 | W 8-6 | 17-18 | 4 | 30,567 | Paul Wilson | Garrett Stephenson | Scott Sullivan | Mike Crudale | Scott Williamson | 174 | 222 | -48 |
| 2003-05-09 | vs MIL | 36 | W 7-6 | 18-18 | 4 | 26,320 | Chris Reitsma | Matt Kinney | Brian Reith | Luis Vizcaino | | 181 | 228 | -47 |
| 2003-05-10 | vs MIL | 37 | L 3-9 | 18-19 | 4 | 32,554 | John Riedling | Ben Sheets | Ben Sheets | John Riedling | | 184 | 237 | -53 |
| 2003-05-11 | vs MIL | 38 | W 7-5 | 19-19 | 4 | 24,804 | Jeff Austin | Wayne Franklin | Jeff Austin | Wayne Franklin | Scott Williamson | 191 | 242 | -51 |
| 2003-05-13 | @ SLN | 39 | W 7-2 | 20-19 | 3 | 34,276 | Paul Wilson | Jason Simontacchi | Paul Wilson | Jason Simontacchi | | 198 | 244 | -46 |
| 2003-05-14 | @ SLN | 40 | W 4-0 | 21-19 | 2 | 31,731 | Danny Graves | Matt Morris | Danny Graves | Matt Morris | | 202 | 244 | -42 |
| 2003-05-15 | @ SLN | 41 | L 3-6 | 21-20 | 3 | 37,904 | John Riedling | Garrett Stephenson | Garrett Stephenson | John Riedling | Cal Eldred | 205 | 250 | -45 |
| 2003-05-16 | @ MIL | 42 | L 3-12 | 21-21 | 4 | 13,376 | Ryan Dempster | Wayne Franklin | Wayne Franklin | Ryan Dempster | | 208 | 262 | -54 |
| 2003-05-17 | @ MIL | 43 | L 6-8 | 21-22 | 4 | 16,482 | Jeff Austin | Glendon Rusch | Mike DeJean | Scott Williamson | | 214 | 270 | -56 |
| 2003-05-18 | @ MIL | 44 | W 6-3 | 22-22 | 4 | 14,703 | Paul Wilson | Ruben Quevedo | Scott Sullivan | Mike DeJean | Scott Williamson | 220 | 273 | -53 |
| 2003-05-20 | vs ATL | 45 | W 9-8 | 23-22 | 4 | 24,076 | Danny Graves | Greg Maddux | Scott Sullivan | Roberto Hernandez | Scott Williamson | 229 | 281 | -52 |
| 2003-05-21 | vs ATL | 46 | W 9-3 | 24-22 | 3 | 33,355 | John Riedling | Mike Hampton | Chris Reitsma | Mike Hampton | | 238 | 284 | -46 |
| 2003-05-22 | vs ATL | 47 | L 4-9 | 24-23 | 4 | 28,962 | Ryan Dempster | Shane Reynolds | Shane Reynolds | Ryan Dempster | | 242 | 293 | -51 |
| 2003-05-23 | vs FLO | 48 | L 4-8 | 24-24 | 4 | 30,596 | Jeff Austin | Tommy Phelps | Tommy Phelps | Jeff Austin | | 246 | 301 | -55 |
| 2003-05-24 | vs FLO | 49 | L 4-5 | 24-25 | 4 | 41,285 | Paul Wilson | Brad Penny | Brad Penny | Paul Wilson | Braden Looper | 250 | 306 | -56 |
| 2003-05-25 | vs FLO | 50 | L 2-6 | 24-26 | 4 | 35,073 | Danny Graves | Dontrelle Willis | Dontrelle Willis | Danny Graves | Braden Looper | 252 | 312 | -60 |
| 2003-05-26 | @ ATL | 51 | W 7-6 | 25-26 | 4 | 33,455 | John Riedling | Mike Hampton | Gabe White | Roberto Hernandez | | 259 | 318 | -59 |
| 2003-05-27 | @ ATL | 52 | L 2-3 | 25-27 | 4 | 23,041 | Jimmy Haynes | Shane Reynolds | Trey Hodges | Chris Reitsma | | 261 | 321 | -60 |
| 2003-05-28 | @ ATL | 53 | L 3-15 | 25-28 | 4 | 25,713 | Jeff Austin | Russ Ortiz | Russ Ortiz | Jeff Austin | Jung Bong | 264 | 336 | -72 |
| 2003-05-30 | @ FLO | 54 | W 4-3 | 26-28 | 4 | 17,385 | Paul Wilson | Mark Redman | Gabe White | Armando Almanza | Scott Williamson | 268 | 339 | -71 |
| 2003-05-31 | @ FLO | 55 | L 2-3 | 26-29 | 4 | 16,190 | Danny Graves | Dontrelle Willis | Dontrelle Willis | Danny Graves | Braden Looper | 270 | 342 | -72 |
| 2003-06-01 | @ FLO | 56 | W 9-6 | 27-29 | 4 | 12,236 | John Riedling | Carl Pavano | Scott Sullivan | Carl Pavano | Scott Williamson | 279 | 348 | -69 |
| 2003-06-03 | vs NYA | 57 | W 4-3 | 28-29 | 4 | 41,827 | Jimmy Haynes | Andy Pettitte | Chris Reitsma | Antonio Osuna | | 283 | 351 | -68 |
| 2003-06-04 | vs NYA | 58 | W 6-2 | 29-29 | 4 | 42,082 | Paul Wilson | Mike Mussina | Paul Wilson | Mike Mussina | | 289 | 353 | -64 |
| 2003-06-05 | vs NYA | 59 | L 2-10 | 29-30 | 4 | 42,282 | Danny Graves | Jose Contreras | Jose Contreras | Danny Graves | | 291 | 363 | -72 |
| 2003-06-06 | vs TOR | 60 | L 2-9 | 29-31 | 4 | 28,281 | John Riedling | Roy Halladay | Roy Halladay | John Riedling | | 293 | 372 | -79 |
| 2003-06-07 | vs TOR | 61 | W 9-8 | 30-31 | 4 | 30,158 | Ryan Dempster | Doug Davis | Chris Reitsma | Cliff Politte | | 302 | 380 | -78 |
| 2003-06-08 | vs TOR | 62 | L 0-5 | 30-32 | 4 | 25,633 | Jimmy Haynes | Kelvim Escobar | Kelvim Escobar | Jimmy Haynes | | 302 | 385 | -83 |
| 2003-06-10 | @ TBA | 63 | W 4-2 | 31-32 | 4 | 12,294 | Paul Wilson | Jason Standridge | Paul Wilson | Jason Standridge | Scott Williamson | 306 | 387 | -81 |
| 2003-06-11 | @ TBA | 64 | W 7-6 | 32-32 | 4 | 10,105 | John Riedling | Dewon Brazelton | Chris Reitsma | Jesus Colome | Scott Williamson | 313 | 393 | -80 |
| 2003-06-12 | @ TBA | 65 | W 2-1 | 33-32 | 4 | 10,379 | Ryan Dempster | Geremi Gonzalez | Ryan Dempster | Geremi Gonzalez | Scott Williamson | 315 | 394 | -79 |
| 2003-06-13 | vs PHI | 66 | W 15-1 | 34-32 | 4 | 30,144 | Jimmy Haynes | Kevin Millwood | Jimmy Haynes | Kevin Millwood | | 330 | 395 | -65 |
| 2003-06-14 | vs PHI | 67 | L 2-12 | 34-33 | 4 | 35,398 | Danny Graves | Randy Wolf | Randy Wolf | Danny Graves | | 332 | 407 | -75 |
| 2003-06-16 | vs CHN | 68 | L 3-4 | 34-34 | 4 | 28,669 | Jimmy Anderson | Matt Clement | Matt Clement | Jimmy Anderson | Joe Borowski | 335 | 411 | -76 |
| 2003-06-17 | vs CHN | 69 | W 2-1 | 35-34 | 4 | 28,999 | Ryan Dempster | Carlos Zambrano | Scott Williamson | Mike Remlinger | | 337 | 412 | -75 |
| 2003-06-18 | vs CHN | 70 | L 1-4 | 35-35 | 4 | 39,053 | Jimmy Haynes | Kerry Wood | Kerry Wood | Jimmy Haynes | | 338 | 416 | -78 |
| 2003-06-19 | vs CHN | 71 | W 3-1 | 36-35 | 4 | 41,692 | Paul Wilson | Mark Prior | Paul Wilson | Mark Prior | Scott Williamson | 341 | 417 | -76 |
| 2003-06-20 | @ ARI | 72 | L 5-6 | 36-36 | 4 | 34,842 | Danny Graves | Elmer Dessens | Jose Valverde | Scott Williamson | | 346 | 423 | -77 |
| 2003-06-21 | @ ARI | 73 | L 3-5 | 36-37 | 4 | 40,041 | Jimmy Anderson | John Patterson | John Patterson | Jimmy Anderson | Jose Valverde | 349 | 428 | -79 |
| 2003-06-22 | @ ARI | 74 | L 5-6 | 36-38 | 4 | 35,536 | Ryan Dempster | Andrew Good | Eddie Oropesa | Kent Mercker | Jose Valverde | 354 | 434 | -80 |
| 2003-06-24 | @ SLN | 75 | W 7-4 | 37-38 | 4 | 33,352 | Jimmy Haynes | Brett Tomko | Felix Heredia | Jeff Fassero | Danny Graves | 361 | 438 | -77 |
| 2003-06-25 | @ SLN | 76 | L 6-9 | 37-39 | 4 | 34,863 | Paul Wilson | Matt Morris | Matt Morris | Paul Wilson | Jason Isringhausen | 367 | 447 | -80 |
| 2003-06-26 | @ SLN | 77 | L 7-11 | 37-40 | 4 | 34,738 | Jimmy Anderson | Woody Williams | Woody Williams | Jimmy Anderson | | 374 | 458 | -84 |
| 2003-06-27 | @ CLE | 78 | L 0-3 | 37-41 | 4 | 29,233 | Danny Graves | Billy Traber | Billy Traber | Danny Graves | Danys Baez | 374 | 461 | -87 |
| 2003-06-28 | @ CLE | 79 | W 5-4 | 38-41 | 4 | 31,924 | Ryan Dempster | CC Sabathia | Chris Reitsma | Danys Baez | Scott Williamson | 379 | 465 | -86 |
| 2003-06-29 | @ CLE | 80 | L 1-3 | 38-42 | 4 | 28,433 | Jimmy Haynes | Jason Davis | Jason Davis | Jimmy Haynes | Danys Baez | 380 | 468 | -88 |
| 2003-07-01 | @ PIT | 81 | W 5-3 | 39-42 | 4 | 17,803 | Danny Graves | Jeff D'Amico | Danny Graves | Julian Tavarez | Scott Williamson | 385 | 471 | -86 |
| 2003-07-02 | @ PIT | 82 | W 4-3 | 40-42 | 4 | 15,322 | Paul Wilson | Kip Wells | Felix Heredia | Mike Williams | Scott Williamson | 389 | 474 | -85 |
| 2003-07-03 | @ PIT | 83 | L 7-8 | 40-43 | 4 | 19,947 | Ryan Dempster | Josh Fogg | Josh Fogg | Ryan Dempster | Mike Williams | 396 | 482 | -86 |
| 2003-07-04 | vs NYN | 84 | L 2-7 | 40-44 | 4 | 35,111 | Jimmy Haynes | Tom Glavine | Tom Glavine | Jimmy Haynes | Armando Benitez | 398 | 489 | -91 |
| 2003-07-05 | vs NYN | 85 | L 2-6 | 40-45 | 4 | 41,020 | Danny Graves | Steve Trachsel | Steve Trachsel | Danny Graves | David Weathers | 400 | 495 | -95 |
| 2003-07-06 | vs NYN | 86 | L 5-7 | 40-46 | 4 | 31,054 | Paul Wilson | Aaron Heilman | Jaime Cerda | Brian Reith | Armando Benitez | 405 | 502 | -97 |
| 2003-07-07 | @ HOU | 87 | L 1-7 | 40-47 | 4 | 25,339 | Ryan Dempster | Roy Oswalt | Roy Oswalt | Ryan Dempster | | 406 | 509 | -103 |
| 2003-07-08 | @ HOU | 88 | L 3-6 | 40-48 | 4 | 29,091 | Jimmy Haynes | Tim Redding | Tim Redding | Jimmy Haynes | Billy Wagner | 409 | 515 | -106 |
| 2003-07-09 | @ HOU | 89 | L 2-12 | 40-49 | 4 | 26,034 | Danny Graves | Jeriome Robertson | Jeriome Robertson | Danny Graves | | 411 | 527 | -116 |
| 2003-07-10 | @ HOU | 90 | L 2-11 | 40-50 | 5 | 28,712 | Paul Wilson | Ron Villone | Ron Villone | Paul Wilson | Ricky Stone | 413 | 538 | -125 |
| 2003-07-11 | @ MIL | 91 | W 6-1 | 41-50 | 4 | 28,130 | Ryan Dempster | Ben Sheets | Ryan Dempster | Ben Sheets | | 419 | 539 | -120 |
| 2003-07-12 | @ MIL | 92 | W 5-1 | 42-50 | 4 | 33,977 | Jimmy Haynes | Wayne Franklin | Jimmy Haynes | Wayne Franklin | | 424 | 540 | -116 |
| 2003-07-13 | @ MIL | 93 | W 10-8 | 43-50 | 4 | 23,632 | Danny Graves | Matt Kinney | Felix Heredia | Leo Estrella | | 434 | 548 | -114 |
| 2003-07-17 | vs HOU | 94 | L 4-5 | 43-51 | 4 | 29,366 | Paul Wilson | Jeriome Robertson | Jeriome Robertson | Paul Wilson | Billy Wagner | 438 | 553 | -115 |
| 2003-07-18 | vs HOU | 95 | L 3-5 | 43-52 | 4 | 33,745 | Ryan Dempster | Roy Oswalt | Roy Oswalt | Ryan Dempster | Billy Wagner | 441 | 558 | -117 |
| 2003-07-19 | vs HOU | 96 | L 8-9 | 43-53 | 4 | 41,772 | Jimmy Haynes | Ron Villone | Ron Villone | Jimmy Haynes | Octavio Dotel | 449 | 567 | -118 |
| 2003-07-20 | vs HOU | 97 | L 3-6 | 43-54 | 5 | 32,062 | Danny Graves | Wade Miller | Wade Miller | Danny Graves | Billy Wagner | 452 | 573 | -121 |
| 2003-07-21 | vs MIL | 98 | W 11-2 | 44-54 | 5 | 22,630 | Jose Acevedo | Matt Kinney | Jose Acevedo | Matt Kinney | | 463 | 575 | -112 |
| 2003-07-22 | vs MIL | 99 | L 4-6 | 44-55 | 5 | 22,336 | Paul Wilson | Wayne Franklin | Wayne Franklin | Paul Wilson | Danny Kolb | 467 | 581 | -114 |
| 2003-07-23 | vs PIT | 100 | L 5-6 | 44-56 | 5 | 27,629 | Ryan Dempster | Jeff Suppan | Brian Boehringer | Kent Mercker | Mike Lincoln | 472 | 587 | -115 |
| 2003-07-24 | vs PIT | 101 | L 5-7 | 44-57 | 5 | 35,504 | Jimmy Haynes | Jeff D'Amico | Mike Lincoln | Chris Reitsma | | 477 | 594 | -117 |
| 2003-07-25 | @ NYN | 102 | L 1-3 | 44-58 | 5 | 34,021 | Danny Graves | Al Leiter | Al Leiter | Danny Graves | Mike Stanton | 478 | 597 | -119 |
| 2003-07-26 | @ NYN | 103 | W 8-3 | 45-58 | 5 | 29,305 | Jose Acevedo | Aaron Heilman | Jose Acevedo | Aaron Heilman | | 486 | 600 | -114 |
| 2003-07-27 | @ NYN | 104 | W 8-5 | 46-58 | 5 | 30,173 | Paul Wilson | Steve Trachsel | Paul Wilson | Steve Trachsel | Scott Williamson | 494 | 605 | -111 |
| 2003-07-28 | vs PHI | 105 | W 6-5 | 47-58 | 5 | 29,200 | Ryan Dempster | Randy Wolf | Scott Williamson | Terry Adams | | 500 | 610 | -110 |
| 2003-07-29 | vs COL | 106 | L 3-5 | 47-59 | 5 | 25,663 | Jimmy Haynes | Darren Oliver | Darren Oliver | Jimmy Haynes | Justin Speier | 503 | 615 | -112 |
| 2003-07-30 | vs COL | 107 | W 3-2 | 48-59 | 5 | 23,962 | Danny Graves | Shawn Chacon | Chris Reitsma | Jose Jimenez | | 506 | 617 | -111 |
| 2003-07-31 | vs COL | 108 | W 5-4 | 49-59 | 5 | 24,861 | Jose Acevedo | Chin-hui Tsao | John Riedling | Brian Fuentes | | 511 | 621 | -110 |
| 2003-08-01 | vs SFN | 109 | W 5-3 | 50-59 | 5 | 39,291 | Paul Wilson | Jerome Williams | Chris Reitsma | Felix Rodriguez | | 516 | 624 | -108 |
| 2003-08-02 | vs SFN | 110 | W 5-4 | 51-59 | 5 | 36,682 | Josh Hall | Jesse Foppert | Ryan Wagner | Felix Rodriguez | Felix Heredia | 521 | 628 | -107 |
| 2003-08-03 | vs SFN | 111 | L 3-7 | 51-60 | 5 | 35,840 | Jimmy Haynes | Dustin Hermanson | Dustin Hermanson | Jimmy Haynes | | 524 | 635 | -111 |
| 2003-08-05 | @ LAN | 112 | L 2-5 | 51-61 | 5 | 37,744 | Danny Graves | Kevin Brown | Kevin Brown | Danny Graves | Eric Gagne | 526 | 640 | -114 |
| 2003-08-06 | @ LAN | 113 | L 1-2 | 51-62 | 5 | 31,828 | Jose Acevedo | Odalis Perez | Odalis Perez | Felix Heredia | Eric Gagne | 527 | 642 | -115 |
| 2003-08-07 | @ LAN | 114 | L 3-4 | 51-63 | 5 | 30,625 | Paul Wilson | Hideo Nomo | Hideo Nomo | Paul Wilson | Eric Gagne | 530 | 646 | -116 |
| 2003-08-08 | @ SDN | 115 | L 0-1 | 51-64 | 5 | 24,543 | John Bale | Jake Peavy | Rod Beck | Brian Reith | | 530 | 647 | -117 |
| 2003-08-09 | @ SDN | 116 | W 9-5 | 52-64 | 5 | 36,745 | Aaron Harang | Oliver Perez | Aaron Harang | Oliver Perez | | 539 | 652 | -113 |
| 2003-08-10 | @ SDN | 117 | L 0-2 | 52-65 | 5 | 24,141 | Danny Graves | Brian Lawrence | Brian Lawrence | Danny Graves | Rod Beck | 539 | 654 | -115 |
| 2003-08-12 | vs ARI | 118 | L 0-2 | 52-66 | 5 | 31,485 | Paul Wilson | Curt Schilling | Curt Schilling | Paul Wilson | Matt Mantei | 539 | 656 | -117 |
| 2003-08-13 | vs ARI | 119 | L 1-3 | 52-67 | 5 | 23,309 | John Bale | Miguel Batista | Steve Randolph | Felix Heredia | Matt Mantei | 540 | 659 | -119 |
| 2003-08-14 | vs ARI | 120 | W 3-2 | 53-67 | 5 | 25,056 | Aaron Harang | Brandon Webb | Aaron Harang | Brandon Webb | Chris Reitsma | 543 | 661 | -118 |
| 2003-08-15 | vs HOU | 121 | W 9-7 | 54-67 | 5 | 33,349 | Danny Graves | Ron Villone | Ryan Wagner | Brad Lidge | | 552 | 668 | -116 |
| 2003-08-16 | vs HOU | 122 | L 2-5 | 54-68 | 5 | 29,902 | Seth Etherton | Wade Miller | Wade Miller | Seth Etherton | Billy Wagner | 554 | 673 | -119 |
| 2003-08-17 | vs HOU | 123 | W 4-3 | 55-68 | 5 | 28,576 | Paul Wilson | Tim Redding | Paul Wilson | Tim Redding | Chris Reitsma | 558 | 676 | -118 |
| 2003-08-19 | @ ARI | 124 | L 1-6 | 55-69 | 5 | 34,869 | John Bale | Brandon Webb | Brandon Webb | John Bale | Matt Mantei | 559 | 682 | -123 |
| 2003-08-20 | @ ARI | 125 | W 2-0 | 56-69 | 5 | 28,377 | Aaron Harang | Randy Johnson | Aaron Harang | Randy Johnson | Chris Reitsma | 561 | 682 | -121 |
| 2003-08-21 | @ ARI | 126 | L 3-9 | 56-70 | 5 | 27,796 | Danny Graves | Elmer Dessens | Elmer Dessens | Danny Graves | | 564 | 691 | -127 |
| 2003-08-22 | @ HOU | 127 | W 4-3 | 57-70 | 5 | 26,627 | Seth Etherton | Wade Miller | Seth Etherton | Wade Miller | Chris Reitsma | 568 | 694 | -126 |
| 2003-08-23 | @ HOU | 128 | W 3-1 | 58-70 | 5 | 32,560 | Paul Wilson | Tim Redding | Paul Wilson | Tim Redding | Chris Reitsma | 571 | 695 | -124 |
| 2003-08-24 | @ HOU | 129 | L 3-6 | 58-71 | 5 | 35,730 | John Bale | Jeriome Robertson | Jeriome Robertson | Brian Reith | Billy Wagner | 574 | 701 | -127 |
| 2003-08-25 | vs MIL | 130 | L 6-10 | 58-72 | 5 | 18,411 | Aaron Harang | Matt Kinney | Matt Kinney | Aaron Harang | Danny Kolb | 580 | 711 | -131 |
| 2003-08-26 | vs MIL | 131 | L 1-7 | 58-73 | 5 | 18,787 | Dan Serafini | Doug Davis | Doug Davis | Dan Serafini | | 581 | 718 | -137 |
| 2003-08-27 | vs MIL | 132 | L 2-6 | 58-74 | 5 | 18,069 | Seth Etherton | Wayne Franklin | Wayne Franklin | Seth Etherton | | 583 | 724 | -141 |
| 2003-08-28 | vs MIL | 133 | L 3-4 | 58-75 | 5 | 21,870 | Paul Wilson | Wes Obermueller | Valerio de los Santos | Chris Reitsma | Danny Kolb | 586 | 728 | -142 |
| 2003-08-29 | vs SLN | 134 | W 8-5 | 59-75 | 5 | 27,121 | John Bale | Dan Haren | John Bale | Dan Haren | Danny Graves | 594 | 733 | -139 |
| 2003-08-30 | vs SLN | 135 | L 3-6 | 59-76 | 5 | 39,380 | Aaron Harang | Brett Tomko | Brett Tomko | Aaron Harang | Jason Isringhausen | 597 | 739 | -142 |
| 2003-08-31 | vs SLN | 136 | L 0-5 | 59-77 | 6 | 29,272 | Dan Serafini | Sterling Hitchcock | Sterling Hitchcock | Dan Serafini | | 597 | 744 | -147 |
| 2003-09-01 | @ MIL | 137 | W 5-4 | 60-77 | 5 | 19,588 | Seth Etherton | Wayne Franklin | Seth Etherton | Wayne Franklin | Chris Reitsma | 602 | 748 | -146 |
| 2003-09-02 | @ MIL | 138 | L 3-4 | 60-78 | 6 | 8,703 | Paul Wilson | Wes Obermueller | Luis Vizcaino | Danny Graves | Danny Kolb | 605 | 752 | -147 |
| 2003-09-03 | @ MIL | 139 | L 6-9 | 60-79 | 6 | 10,282 | John Bale | Luis Martinez | Leo Estrella | Scott Randall | Danny Kolb | 611 | 761 | -150 |
| 2003-09-05 | @ SLN | 140 | W 4-2 | 61-79 | 6 | 29,608 | Aaron Harang | Sterling Hitchcock | Scott Randall | Jason Simontacchi | Chris Reitsma | 615 | 763 | -148 |
| 2003-09-06 | @ SLN | 141 | L 6-13 | 61-80 | 6 | 39,718 | Dan Serafini | Woody Williams | Woody Williams | Dan Serafini | | 621 | 776 | -155 |
| 2003-09-07 | @ SLN | 142 | L 0-9 | 61-81 | 6 | 34,389 | Seth Etherton | Matt Morris | Matt Morris | Seth Etherton | | 621 | 785 | -164 |
| 2003-09-08 | vs PIT | 143 | L 1-9 | 61-82 | 6 | 19,073 | John Bale | Josh Fogg | Josh Fogg | John Bale | | 622 | 794 | -172 |
| 2003-09-09 | vs PIT | 144 | W 10-6 | 62-82 | 5 | 21,241 | Josh Hall | Salomon Torres | Matt Belisle | Brian Boehringer | | 632 | 800 | -168 |
| 2003-09-10 | vs PIT | 145 | L 2-3 | 62-83 | 5 | 20,560 | Todd Van Poppel | Oliver Perez | Mike Lincoln | Chris Reitsma | Julian Tavarez | 634 | 803 | -169 |
| 2003-09-11 | vs PIT | 146 | W 3-2 | 63-83 | 5 | 20,479 | Dan Serafini | Jeff D'Amico | Scott Randall | Jeff D'Amico | Chris Reitsma | 637 | 805 | -168 |
| 2003-09-12 | @ CHN | 147 | L 6-7 | 63-84 | 5 | 38,219 | Seth Etherton | Kerry Wood | Antonio Alfonseca | Scott Randall | Joe Borowski | 643 | 812 | -169 |
| 2003-09-13 | @ CHN | 148 | L 6-9 | 63-85 | 6 | 39,983 | John Bale | Juan Cruz | Antonio Alfonseca | Matt Belisle | Joe Borowski | 649 | 821 | -172 |
| 2003-09-14 | @ CHN | 149 | W 1-0 | 64-85 | 5 | 38,827 | Josh Hall | Carlos Zambrano | John Riedling | Carlos Zambrano | Chris Reitsma | 650 | 821 | -171 |
| 2003-09-15 | @ PIT | 150 | L 3-6 | 64-86 | 5 | 8,565 | Todd Van Poppel | Ryan Vogelsong | Ryan Vogelsong | Todd Van Poppel | Julian Tavarez | 653 | 827 | -174 |
| 2003-09-16 | @ PIT | 151 | W 12-4 | 65-86 | 5 | 11,995 | Aaron Harang | Oliver Perez | Aaron Harang | Oliver Perez | Brian Reith | 665 | 831 | -166 |
| 2003-09-17 | @ PIT | 152 | L 5-8 | 65-87 | 5 | 10,625 | Seth Etherton | Jeff D'Amico | Jeff D'Amico | Seth Etherton | Julian Tavarez | 670 | 839 | -169 |
| 2003-09-18 | @ PIT | 153 | L 0-7 | 65-88 | 5 | 10,390 | John Bale | Kip Wells | Kip Wells | Scott Randall | | 670 | 846 | -176 |
| 2003-09-19 | @ PHI | 154 | L 3-7 | 65-89 | 5 | 30,191 | Josh Hall | Randy Wolf | Randy Wolf | Josh Hall | | 673 | 853 | -180 |
| 2003-09-20 | @ PHI | 155 | W 2-0 | 66-89 | 5 | 35,239 | Todd Van Poppel | Amaury Telemaco | Todd Van Poppel | Amaury Telemaco | Chris Reitsma | 675 | 853 | -178 |
| 2003-09-21 | @ PHI | 156 | W 4-3 | 67-89 | 5 | 57,883 | Aaron Harang | Vicente Padilla | Dan Serafini | Vicente Padilla | Chris Reitsma | 679 | 856 | -177 |
| 2003-09-23 | vs CHN | 157 | L 0-6 | 67-90 | 5 | 26,124 | Scott Randall | Kerry Wood | Kerry Wood | Scott Randall | | 679 | 862 | -183 |
| 2003-09-24 | vs CHN | 158 | L 0-8 | 67-91 | 5 | 27,021 | Josh Hall | Shawn Estes | Shawn Estes | Josh Hall | | 679 | 870 | -191 |
| 2003-09-25 | vs CHN | 159 | W 9-7 | 68-91 | 5 | 36,963 | Todd Van Poppel | Carlos Zambrano | Todd Van Poppel | Carlos Zambrano | Chris Reitsma | 688 | 877 | -189 |
| 2003-09-26 | vs MON | 160 | L 1-5 | 68-92 | 5 | 28,870 | Aaron Harang | Tomo Ohka | Tomo Ohka | Aaron Harang | | 689 | 882 | -193 |
| 2003-09-27 | vs MON | 161 | W 4-2 | 69-92 | 5 | 31,199 | Brian Reith | Livan Hernandez | Brian Reith | Livan Hernandez | | 693 | 884 | -191 |
| 2003-09-28 | vs MON | 162 | L 1-2 | 69-93 | 5 | 32,322 | Scott Randall | Claudio Vargas | T.J. Tucker | Scott Randall | Rocky Biddle | 694 | 886 | -192 |