| 2003-04-01 | @ HOU | 1 | L 4-10 | 0-1 | 4 | 43,241 | Jason Jennings | Roy Oswalt | Roy Oswalt | Jason Jennings | | 4 | 10 | -6 |
| 2003-04-02 | @ HOU | 2 | L 7-8 | 0-2 | 4 | 21,082 | Aaron Cook | Wade Miller | Billy Wagner | Jose Jimenez | | 11 | 18 | -7 |
| 2003-04-03 | @ HOU | 3 | W 10-5 | 1-2 | 4 | 21,171 | Nelson Cruz | Jeriome Robertson | Nelson Cruz | Jeriome Robertson | | 21 | 23 | -2 |
| 2003-04-04 | vs ARI | 4 | W 2-1 | 2-2 | 2 | 48,087 | Shawn Chacon | Byung-Hyun Kim | Shawn Chacon | Byung-Hyun Kim | Jose Jimenez | 23 | 24 | -1 |
| 2003-04-05 | vs ARI | 5 | W 4-3 | 3-2 | 2 | 25,197 | Darren Oliver | Randy Johnson | Steve Reed | Miguel Batista | | 27 | 27 | 0 |
| 2003-04-06 | vs ARI | 6 | W 8-3 | 4-2 | 2 | 25,443 | Jason Jennings | Curt Schilling | Jason Jennings | Curt Schilling | | 35 | 30 | 5 |
| 2003-04-08 | vs SLN | 7 | L 12-15 | 4-3 | 2 | 21,563 | Aaron Cook | Jason Simontacchi | Cal Eldred | Dan Miceli | | 47 | 45 | 2 |
| 2003-04-09 | vs SLN | 8 | W 9-4 | 5-3 | 2 | 24,110 | Nelson Cruz | Brett Tomko | Nelson Cruz | Brett Tomko | | 56 | 49 | 7 |
| 2003-04-10 | vs SLN | 9 | W 7-6 | 6-3 | 2 | 24,586 | Shawn Chacon | Garrett Stephenson | Javier Lopez | Steve Kline | Jose Jimenez | 63 | 55 | 8 |
| 2003-04-11 | @ SDN | 10 | L 4-6 | 6-4 | 2 | 21,190 | Darren Oliver | Brian Lawrence | Brian Lawrence | Darren Oliver | Brandon Villafuerte | 67 | 61 | 6 |
| 2003-04-12 | @ SDN | 11 | W 3-2 | 7-4 | 2 | 30,830 | Jason Jennings | Adam Eaton | Justin Speier | Brandon Villafuerte | Jose Jimenez | 70 | 63 | 7 |
| 2003-04-13 | @ SDN | 12 | L 2-6 | 7-5 | 2 | 20,316 | Aaron Cook | Oliver Perez | Jaret Wright | Aaron Cook | | 72 | 69 | 3 |
| 2003-04-14 | @ ARI | 13 | W 5-3 | 8-5 | 2 | 25,688 | Nelson Cruz | Byung-Hyun Kim | Nelson Cruz | Byung-Hyun Kim | Jose Jimenez | 77 | 72 | 5 |
| 2003-04-15 | @ ARI | 14 | W 12-1 | 9-5 | 2 | 31,182 | Shawn Chacon | John Patterson | Shawn Chacon | John Patterson | | 89 | 73 | 16 |
| 2003-04-16 | @ ARI | 15 | L 3-4 | 9-6 | 2 | 28,588 | Darren Oliver | Miguel Batista | Matt Mantei | Jose Jimenez | | 92 | 77 | 15 |
| 2003-04-17 | @ ARI | 16 | L 2-11 | 9-7 | 2 | 32,507 | Jason Jennings | Curt Schilling | Curt Schilling | Jason Jennings | | 94 | 88 | 6 |
| 2003-04-18 | vs SDN | 17 | W 12-1 | 10-7 | 2 | 27,609 | Aaron Cook | Oliver Perez | Aaron Cook | Oliver Perez | | 106 | 89 | 17 |
| 2003-04-19 | vs SDN | 18 | W 10-9 | 11-7 | 2 | 27,031 | Nelson Cruz | Clay Condrey | Steve Reed | Brandon Villafuerte | | 116 | 98 | 18 |
| 2003-04-20 | vs SDN | 19 | W 8-0 | 12-7 | 2 | 28,005 | Shawn Chacon | Jake Peavy | Shawn Chacon | Jake Peavy | | 124 | 98 | 26 |
| 2003-04-22 | @ PHI | 20 | L 2-5 | 12-8 | 2 | 13,431 | Darren Oliver | Kevin Millwood | Kevin Millwood | Darren Oliver | Jose Mesa | 126 | 103 | 23 |
| 2003-04-23 | @ PHI | 21 | L 4-6 | 12-9 | 2 | 13,444 | Jason Jennings | Brett Myers | Brett Myers | Jason Jennings | Jose Mesa | 130 | 109 | 21 |
| 2003-04-24 | @ PHI | 22 | L 1-9 | 12-10 | 2 | 16,947 | Aaron Cook | Randy Wolf | Randy Wolf | Aaron Cook | | 131 | 118 | 13 |
| 2003-04-25 | vs CHN | 23 | L 7-11 | 12-11 | 2 | 32,162 | Nelson Cruz | Mark Prior | Mark Prior | Nelson Cruz | | 138 | 129 | 9 |
| 2003-04-26 | vs CHN | 24 | W 8-5 | 13-11 | 2 | 35,604 | Shawn Chacon | Shawn Estes | Shawn Chacon | Shawn Estes | Jose Jimenez | 146 | 134 | 12 |
| 2003-04-27 | vs CHN | 25 | W 6-3 | 14-11 | 2 | 35,070 | Darren Oliver | Carlos Zambrano | Darren Oliver | Carlos Zambrano | Jose Jimenez | 152 | 137 | 15 |
| 2003-04-29 | vs CIN | 26 | W 10-5 | 15-11 | 2 | 26,206 | Jason Jennings | Chris Reitsma | Jason Jennings | Chris Reitsma | | 162 | 142 | 20 |
| 2003-04-30 | vs CIN | 27 | L 11-13 | 15-12 | 2 | 26,436 | Aaron Cook | Ryan Dempster | Scott Sullivan | Dan Miceli | Scott Williamson | 173 | 155 | 18 |
| 2003-05-01 | vs CIN | 28 | L 2-7 | 15-13 | 2 | 28,788 | Nelson Cruz | Jeff Austin | Jeff Austin | Nelson Cruz | | 175 | 162 | 13 |
| 2003-05-02 | @ CHN | 29 | L 4-7 | 15-14 | 2 | 29,236 | Shawn Chacon | Shawn Estes | Shawn Estes | Shawn Chacon | Joe Borowski | 179 | 169 | 10 |
| 2003-05-03 | @ CHN | 30 | W 6-4 | 16-14 | 2 | 38,332 | Darren Oliver | Carlos Zambrano | Justin Speier | Mark Guthrie | Jose Jimenez | 185 | 173 | 12 |
| 2003-05-04 | @ CHN | 31 | L 4-5 | 16-15 | 2 | 37,223 | Jason Jennings | Kerry Wood | Joe Borowski | Steve Reed | | 189 | 178 | 11 |
| 2003-05-06 | @ ATL | 32 | L 2-3 | 16-16 | 2 | 18,108 | Aaron Cook | Mike Hampton | Roberto Hernandez | Todd Jones | John Smoltz | 191 | 181 | 10 |
| 2003-05-08 | @ ATL | 33 | L 6-12 | 16-18 | 3 | 0 | Nelson Cruz | Shane Reynolds | Shane Reynolds | Nelson Cruz | John Smoltz | 197 | 193 | 4 |
| 2003-05-08 | @ ATL | 34 | L 2-5 | 16-18 | 3 | 22,829 | Shawn Chacon | Russ Ortiz | Russ Ortiz | Shawn Chacon | John Smoltz | 199 | 198 | 1 |
| 2003-05-09 | @ FLO | 35 | L 4-5 | 16-19 | 3 | 10,272 | Darren Oliver | Dontrelle Willis | Braden Looper | Justin Speier | | 203 | 203 | 0 |
| 2003-05-10 | @ FLO | 36 | W 5-4 | 17-19 | 3 | 16,543 | Jason Jennings | Michael Tejera | Jason Jennings | Michael Tejera | Jose Jimenez | 208 | 207 | 1 |
| 2003-05-11 | @ FLO | 37 | L 2-7 | 17-20 | 3 | 9,205 | Aaron Cook | Carl Pavano | Carl Pavano | Aaron Cook | | 210 | 214 | -4 |
| 2003-05-12 | vs NYN | 38 | L 6-9 | 17-21 | 4 | 25,433 | Jason Young | Steve Trachsel | Steve Trachsel | Jason Young | Armando Benitez | 216 | 223 | -7 |
| 2003-05-13 | vs NYN | 39 | W 9-8 | 18-21 | 4 | 25,043 | Shawn Chacon | Tom Glavine | Steve Reed | Jaime Cerda | Jose Jimenez | 225 | 231 | -6 |
| 2003-05-14 | vs NYN | 40 | W 6-5 | 19-21 | 4 | 26,755 | Darren Oliver | Jae Weong Seo | Steve Reed | Mike Stanton | Jose Jimenez | 231 | 236 | -5 |
| 2003-05-15 | vs MON | 41 | W 4-2 | 20-21 | 3 | 23,197 | Jason Jennings | Javier Vazquez | Todd Jones | T.J. Tucker | Jose Jimenez | 235 | 238 | -3 |
| 2003-05-16 | vs MON | 42 | L 1-4 | 20-22 | 3 | 27,117 | Aaron Cook | Livan Hernandez | Luis Ayala | Nelson Cruz | Rocky Biddle | 236 | 242 | -6 |
| 2003-05-17 | vs MON | 43 | L 4-6 | 20-23 | 3 | 30,052 | Jason Young | Zach Day | Luis Ayala | Todd Jones | Rocky Biddle | 240 | 248 | -8 |
| 2003-05-18 | vs MON | 44 | W 4-0 | 21-23 | 3 | 30,720 | Shawn Chacon | Tomo Ohka | Shawn Chacon | Tomo Ohka | | 244 | 248 | -4 |
| 2003-05-20 | @ LAN | 45 | L 1-3 | 21-24 | 3 | 27,251 | Darren Oliver | Kevin Brown | Kevin Brown | Darren Oliver | Eric Gagne | 245 | 251 | -6 |
| 2003-05-21 | @ LAN | 46 | L 2-3 | 21-25 | 3 | 25,332 | Jason Jennings | Kazuhisa Ishii | Kazuhisa Ishii | Jason Jennings | Eric Gagne | 247 | 254 | -7 |
| 2003-05-22 | @ LAN | 47 | L 3-4 | 21-26 | 4 | 27,461 | Aaron Cook | Darren Dreifort | Darren Dreifort | Aaron Cook | Eric Gagne | 250 | 258 | -8 |
| 2003-05-23 | vs SFN | 48 | W 10-7 | 22-26 | 4 | 30,043 | Shawn Chacon | Damian Moss | Shawn Chacon | Damian Moss | | 260 | 265 | -5 |
| 2003-05-24 | vs SFN | 49 | L 1-5 | 22-27 | 4 | 31,475 | Scott Elarton | Kurt Ainsworth | Kurt Ainsworth | Scott Elarton | | 261 | 270 | -9 |
| 2003-05-25 | vs SFN | 50 | W 5-1 | 23-27 | 4 | 33,723 | Darren Oliver | Jesse Foppert | Darren Oliver | Jesse Foppert | | 266 | 271 | -5 |
| 2003-05-26 | vs SFN | 51 | W 12-7 | 24-27 | 4 | 28,340 | Jason Jennings | Kirk Rueter | Brian Fuentes | Joe Nathan | | 278 | 278 | 0 |
| 2003-05-27 | vs LAN | 52 | W 7-3 | 25-27 | 3 | 26,465 | Aaron Cook | Kazuhisa Ishii | Aaron Cook | Kazuhisa Ishii | | 285 | 281 | 4 |
| 2003-05-28 | vs LAN | 53 | W 6-0 | 26-27 | 3 | 27,108 | Shawn Chacon | Darren Dreifort | Shawn Chacon | Darren Dreifort | | 291 | 281 | 10 |
| 2003-05-29 | vs LAN | 54 | W 12-5 | 27-27 | 3 | 27,007 | Scott Elarton | Odalis Perez | Scott Elarton | Odalis Perez | | 303 | 286 | 17 |
| 2003-05-30 | @ SFN | 55 | L 2-6 | 27-28 | 3 | 38,439 | Darren Oliver | Kurt Ainsworth | Kurt Ainsworth | Darren Oliver | | 305 | 292 | 13 |
| 2003-05-31 | @ SFN | 56 | L 1-2 | 27-29 | 3 | 40,256 | Jason Jennings | Jesse Foppert | Jesse Foppert | Jason Jennings | Tim Worrell | 306 | 294 | 12 |
| 2003-06-01 | @ SFN | 57 | L 0-4 | 27-30 | 3 | 41,404 | Aaron Cook | Kirk Rueter | Kirk Rueter | Aaron Cook | | 306 | 298 | 8 |
| 2003-06-02 | @ SFN | 58 | W 4-1 | 28-30 | 3 | 34,231 | Shawn Chacon | Jason Schmidt | Shawn Chacon | Jason Schmidt | Jose Jimenez | 310 | 299 | 11 |
| 2003-06-03 | vs CLE | 59 | W 7-3 | 29-30 | 3 | 22,326 | Scott Elarton | Ricardo Rodriguez | Scott Elarton | Ricardo Rodriguez | | 317 | 302 | 15 |
| 2003-06-04 | vs CLE | 60 | W 2-1 | 30-30 | 3 | 22,222 | Darren Oliver | Billy Traber | Darren Oliver | Billy Traber | Jose Jimenez | 319 | 303 | 16 |
| 2003-06-05 | vs CLE | 61 | W 7-4 | 31-30 | 3 | 25,221 | Jason Jennings | CC Sabathia | Jason Jennings | CC Sabathia | Jose Jimenez | 326 | 307 | 19 |
| 2003-06-07 | vs KCA | 62 | L 11-13 | 31-32 | 3 | 25,421 | Shawn Chacon | Chris George | Chris George | Shawn Chacon | Mike MacDougal | 337 | 320 | 17 |
| 2003-06-07 | vs KCA | 63 | L 5-9 | 31-32 | 3 | 26,435 | Todd Jones | D.J. Carrasco | Jason Gilfillan | Todd Jones | | 342 | 329 | 13 |
| 2003-06-08 | vs KCA | 64 | W 8-7 | 32-32 | 3 | 30,084 | Scott Elarton | Jeremy Affeldt | Scott Elarton | Rick DeHart | Jose Jimenez | 350 | 336 | 14 |
| 2003-06-10 | @ MIN | 65 | W 5-0 | 33-32 | 3 | 18,886 | Jason Jennings | Brad Radke | Jason Jennings | Brad Radke | | 355 | 336 | 19 |
| 2003-06-11 | @ MIN | 66 | L 4-7 | 33-33 | 3 | 17,942 | Aaron Cook | Kyle Lohse | Kyle Lohse | Aaron Cook | Eddie Guardado | 359 | 343 | 16 |
| 2003-06-12 | @ MIN | 67 | L 3-15 | 33-34 | 3 | 18,003 | Darren Oliver | Kenny Rogers | Kenny Rogers | Darren Oliver | | 362 | 358 | 4 |
| 2003-06-13 | @ DET | 68 | W 7-2 | 34-34 | 3 | 19,212 | Shawn Chacon | Nate Cornejo | Shawn Chacon | Nate Cornejo | | 369 | 360 | 9 |
| 2003-06-14 | @ DET | 69 | L 7-9 | 34-35 | 3 | 19,260 | Scott Elarton | Mike Maroth | Wil Ledezma | Scott Elarton | Chris Spurling | 376 | 369 | 7 |
| 2003-06-15 | @ DET | 70 | W 5-4 | 35-35 | 3 | 19,323 | Jason Jennings | Gary Knotts | Jason Jennings | Gary Knotts | Jose Jimenez | 381 | 373 | 8 |
| 2003-06-16 | vs SDN | 71 | L 5-7 | 35-36 | 3 | 22,716 | Aaron Cook | Adam Eaton | Jay Witasick | Jose Jimenez | Rod Beck | 386 | 380 | 6 |
| 2003-06-17 | vs SDN | 72 | L 3-4 | 35-37 | 3 | 22,178 | Denny Neagle | Jake Peavy | Jake Peavy | Denny Neagle | Jay Witasick | 389 | 384 | 5 |
| 2003-06-18 | vs SDN | 73 | W 5-3 | 36-37 | 3 | 22,033 | Shawn Chacon | Kevin Jarvis | Shawn Chacon | Kevin Jarvis | Justin Speier | 394 | 387 | 7 |
| 2003-06-19 | vs SDN | 74 | W 10-5 | 37-37 | 3 | 23,515 | Darren Oliver | Brian Lawrence | Darren Oliver | Brian Lawrence | | 404 | 392 | 12 |
| 2003-06-20 | vs DET | 75 | L 5-7 | 37-38 | 4 | 29,603 | Scott Elarton | Mike Maroth | Mike Maroth | Scott Elarton | | 409 | 399 | 10 |
| 2003-06-21 | vs DET | 76 | W 9-6 | 38-38 | 4 | 35,660 | Jason Jennings | Matt Roney | Jason Jennings | Steve Sparks | | 418 | 405 | 13 |
| 2003-06-22 | vs DET | 77 | W 5-3 | 39-38 | 4 | 34,723 | Denny Neagle | Adam Bernero | Denny Neagle | Adam Bernero | Jose Jimenez | 423 | 408 | 15 |
| 2003-06-23 | @ SDN | 78 | W 5-1 | 40-38 | 4 | 18,072 | Shawn Chacon | Kevin Jarvis | Shawn Chacon | Kevin Jarvis | | 428 | 409 | 19 |
| 2003-06-24 | @ SDN | 79 | W 5-2 | 41-38 | 4 | 15,915 | Darren Oliver | Brian Lawrence | Darren Oliver | Brian Lawrence | Jose Jimenez | 433 | 411 | 22 |
| 2003-06-25 | @ SDN | 80 | L 6-7 | 41-39 | 4 | 19,908 | Scott Elarton | Oliver Perez | Luther Hackman | Todd Jones | Rod Beck | 439 | 418 | 21 |
| 2003-06-27 | @ PIT | 81 | L 3-5 | 41-40 | 4 | 37,566 | Jason Jennings | Josh Fogg | Josh Fogg | Jason Jennings | Mike Williams | 442 | 423 | 19 |
| 2003-06-28 | @ PIT | 82 | W 5-4 | 42-40 | 4 | 25,083 | Denny Neagle | Kris Benson | Denny Neagle | Kris Benson | Jose Jimenez | 447 | 427 | 20 |
| 2003-06-29 | @ PIT | 83 | L 0-9 | 42-41 | 4 | 20,475 | Shawn Chacon | Jeff Suppan | Jeff Suppan | Shawn Chacon | | 447 | 436 | 11 |
| 2003-06-30 | vs ARI | 84 | L 7-8 | 42-42 | 4 | 33,533 | Darren Oliver | Elmer Dessens | Steve Randolph | Jose Jimenez | | 454 | 444 | 10 |
| 2003-07-01 | vs ARI | 85 | W 7-4 | 43-42 | 4 | 25,209 | Denny Stark | Andrew Good | Javier Lopez | Andrew Good | Justin Speier | 461 | 448 | 13 |
| 2003-07-02 | vs ARI | 86 | W 6-2 | 44-42 | 4 | 47,032 | Jason Jennings | John Patterson | Jason Jennings | John Patterson | Brian Fuentes | 467 | 450 | 17 |
| 2003-07-03 | vs ARI | 87 | L 4-8 | 44-43 | 4 | 48,560 | Denny Neagle | Brandon Webb | Brandon Webb | Denny Neagle | | 471 | 458 | 13 |
| 2003-07-04 | @ MIL | 88 | W 8-6 | 45-43 | 4 | 21,144 | Aaron Cook | Dave Burba | Steve Reed | Leo Estrella | Justin Speier | 479 | 464 | 15 |
| 2003-07-05 | @ MIL | 89 | W 9-8 | 46-43 | 4 | 30,731 | Darren Oliver | Matt Ford | Darren Oliver | Matt Ford | Brian Fuentes | 488 | 472 | 16 |
| 2003-07-06 | @ MIL | 90 | L 1-3 | 46-44 | 4 | 21,623 | Denny Stark | Ben Sheets | Ben Sheets | Jose Jimenez | Mike DeJean | 489 | 475 | 14 |
| 2003-07-07 | @ ARI | 91 | L 6-14 | 46-45 | 4 | 32,019 | Jason Jennings | John Patterson | Steve Randolph | Nelson Cruz | | 495 | 489 | 6 |
| 2003-07-08 | @ ARI | 92 | L 3-9 | 46-46 | 4 | 36,436 | Denny Neagle | Brandon Webb | Brandon Webb | Steve Reed | | 498 | 498 | 0 |
| 2003-07-09 | vs SFN | 93 | W 11-7 | 47-46 | 4 | 31,139 | Aaron Cook | Jesse Foppert | Aaron Cook | Jesse Foppert | | 509 | 505 | 4 |
| 2003-07-10 | vs SFN | 94 | W 11-3 | 48-46 | 4 | 30,954 | Darren Oliver | Brian Powell | Darren Oliver | Brian Powell | | 520 | 508 | 12 |
| 2003-07-11 | vs LAN | 95 | W 7-6 | 49-46 | 4 | 34,150 | Denny Stark | Hideo Nomo | Brian Fuentes | Paul Shuey | Justin Speier | 527 | 514 | 13 |
| 2003-07-12 | vs LAN | 96 | W 5-3 | 50-46 | 4 | 41,696 | Jason Jennings | Andy Ashby | Jason Jennings | Andy Ashby | Justin Speier | 532 | 517 | 15 |
| 2003-07-13 | vs LAN | 97 | L 3-9 | 50-47 | 4 | 32,483 | Denny Neagle | Wilson Alvarez | Wilson Alvarez | Denny Neagle | | 535 | 526 | 9 |
| 2003-07-17 | @ SFN | 98 | L 4-8 | 50-48 | 4 | 41,052 | Jason Jennings | Damian Moss | Damian Moss | Jason Jennings | | 539 | 534 | 5 |
| 2003-07-18 | @ SFN | 99 | L 0-7 | 50-49 | 4 | 41,690 | Darren Oliver | Jim Brower | Jim Brower | Darren Oliver | | 539 | 541 | -2 |
| 2003-07-19 | @ SFN | 100 | L 3-5 | 50-50 | 4 | 42,607 | Shawn Chacon | Jason Schmidt | Jason Schmidt | Shawn Chacon | Tim Worrell | 542 | 546 | -4 |
| 2003-07-20 | @ SFN | 101 | L 4-8 | 50-51 | 4 | 42,620 | Denny Neagle | Jesse Foppert | Jesse Foppert | Denny Neagle | | 546 | 554 | -8 |
| 2003-07-21 | @ LAN | 102 | W 4-1 | 51-51 | 4 | 27,243 | Denny Stark | Andy Ashby | Denny Stark | Andy Ashby | | 550 | 555 | -5 |
| 2003-07-22 | @ LAN | 103 | L 2-5 | 51-52 | 4 | 30,416 | Jason Jennings | Hideo Nomo | Hideo Nomo | Jason Jennings | Eric Gagne | 552 | 560 | -8 |
| 2003-07-23 | @ LAN | 104 | W 8-3 | 52-52 | 4 | 33,589 | Darren Oliver | Kazuhisa Ishii | Darren Oliver | Kazuhisa Ishii | | 560 | 563 | -3 |
| 2003-07-24 | @ LAN | 105 | L 0-1 | 52-53 | 4 | 33,144 | Shawn Chacon | Kevin Brown | Paul Shuey | Javier Lopez | | 560 | 564 | -4 |
| 2003-07-25 | vs MIL | 106 | W 7-3 | 53-53 | 4 | 39,013 | Chin-hui Tsao | Wes Obermueller | Chin-hui Tsao | Wes Obermueller | | 567 | 567 | 0 |
| 2003-07-26 | vs MIL | 107 | W 13-8 | 54-53 | 4 | 40,675 | Denny Stark | Matt Kinney | Aaron Cook | Valerio de los Santos | | 580 | 575 | 5 |
| 2003-07-27 | vs MIL | 108 | W 6-1 | 55-53 | 4 | 30,108 | Jason Jennings | Wayne Franklin | Jason Jennings | Wayne Franklin | | 586 | 576 | 10 |
| 2003-07-29 | @ CIN | 109 | W 5-3 | 56-53 | 4 | 25,663 | Darren Oliver | Jimmy Haynes | Darren Oliver | Jimmy Haynes | Justin Speier | 591 | 579 | 12 |
| 2003-07-30 | @ CIN | 110 | L 2-3 | 56-54 | 4 | 23,962 | Shawn Chacon | Danny Graves | Chris Reitsma | Jose Jimenez | | 593 | 582 | 11 |
| 2003-07-31 | @ CIN | 111 | L 4-5 | 56-55 | 4 | 24,861 | Chin-hui Tsao | Jose Acevedo | John Riedling | Brian Fuentes | | 597 | 587 | 10 |
| 2003-08-01 | @ PIT | 112 | L 11-12 | 56-56 | 3 | 22,413 | Denny Stark | Salomon Torres | Duaner Sanchez | Adam Bernero | | 608 | 599 | 9 |
| 2003-08-02 | @ PIT | 113 | L 0-1 | 56-57 | 3 | 37,820 | Jason Jennings | Brian Meadows | Brian Meadows | Jason Jennings | Mike Lincoln | 608 | 600 | 8 |
| 2003-08-03 | @ PIT | 114 | W 16-4 | 57-57 | 3 | 16,839 | Darren Oliver | Jeff D'Amico | Darren Oliver | Jeff D'Amico | Jose Jimenez | 624 | 604 | 20 |
| 2003-08-05 | vs PHI | 115 | L 2-7 | 57-58 | 4 | 28,034 | Shawn Chacon | Brett Myers | Brett Myers | Shawn Chacon | | 626 | 611 | 15 |
| 2003-08-06 | vs PHI | 116 | W 5-1 | 58-58 | 4 | 27,599 | Chin-hui Tsao | Brandon Duckworth | Chin-hui Tsao | Brandon Duckworth | | 631 | 612 | 19 |
| 2003-08-07 | vs PHI | 117 | W 4-3 | 59-58 | 4 | 27,855 | Denny Stark | Kevin Millwood | Javier Lopez | Kevin Millwood | Justin Speier | 635 | 615 | 20 |
| 2003-08-08 | vs PIT | 118 | W 13-6 | 60-58 | 4 | 28,362 | Jason Jennings | Brian Meadows | Jose Jimenez | Pat Mahomes | | 648 | 621 | 27 |
| 2003-08-09 | vs PIT | 119 | L 4-10 | 60-59 | 4 | 34,611 | Darren Oliver | Jeff D'Amico | Jeff D'Amico | Darren Oliver | | 652 | 631 | 21 |
| 2003-08-10 | vs PIT | 120 | L 3-5 | 60-60 | 4 | 26,904 | Shawn Chacon | Nelson Figueroa | Nelson Figueroa | Shawn Chacon | Mike Lincoln | 655 | 636 | 19 |
| 2003-08-11 | @ MON | 121 | L 1-3 | 60-61 | 4 | 6,401 | Jason Jennings | Zach Day | Zach Day | Jason Jennings | Rocky Biddle | 656 | 639 | 17 |
| 2003-08-12 | @ MON | 122 | W 6-3 | 61-61 | 4 | 7,277 | Chin-hui Tsao | Tomo Ohka | Brian Fuentes | Rocky Biddle | Javier Lopez | 662 | 642 | 20 |
| 2003-08-13 | @ MON | 123 | L 5-6 | 61-62 | 4 | 6,724 | Denny Stark | Javier Vazquez | Javier Vazquez | Denny Stark | Luis Ayala | 667 | 648 | 19 |
| 2003-08-15 | @ NYN | 124 | L 0-5 | 61-63 | 4 | 28,081 | Darren Oliver | Tom Glavine | Tom Glavine | Darren Oliver | | 667 | 653 | 14 |
| 2003-08-16 | @ NYN | 125 | L 4-13 | 61-64 | 4 | 28,233 | Shawn Chacon | Jae Weong Seo | Jae Weong Seo | Shawn Chacon | | 671 | 666 | 5 |
| 2003-08-17 | @ NYN | 126 | L 4-6 | 61-65 | 4 | 28,393 | Jason Jennings | Al Leiter | Al Leiter | Jason Jennings | David Weathers | 675 | 672 | 3 |
| 2003-08-18 | @ NYN | 127 | L 0-8 | 61-66 | 4 | 23,865 | Chin-hui Tsao | Steve Trachsel | Steve Trachsel | Chin-hui Tsao | | 675 | 680 | -5 |
| 2003-08-19 | vs FLO | 128 | W 10-2 | 62-66 | 4 | 25,889 | Denny Stark | Carl Pavano | Denny Stark | Carl Pavano | | 685 | 682 | 3 |
| 2003-08-20 | vs FLO | 129 | W 9-3 | 63-66 | 4 | 23,534 | Darren Oliver | Mark Redman | Cory Vance | Mark Redman | | 694 | 685 | 9 |
| 2003-08-21 | vs FLO | 130 | W 5-4 | 64-66 | 4 | 23,846 | Jose Jimenez | Brad Penny | Justin Speier | Braden Looper | | 699 | 689 | 10 |
| 2003-08-22 | vs ATL | 131 | L 3-9 | 64-67 | 4 | 35,578 | Jason Jennings | Greg Maddux | Greg Maddux | Jason Jennings | | 702 | 698 | 4 |
| 2003-08-23 | vs ATL | 132 | L 4-5 | 64-68 | 4 | 42,303 | Chin-hui Tsao | Mike Hampton | Mike Hampton | Chin-hui Tsao | John Smoltz | 706 | 703 | 3 |
| 2003-08-24 | vs ATL | 133 | L 6-12 | 64-69 | 4 | 31,227 | Denny Stark | Russ Ortiz | Russ Ortiz | Denny Stark | | 712 | 715 | -3 |
| 2003-08-26 | vs SFN | 134 | L 1-3 | 64-70 | 4 | 24,100 | Darren Oliver | Jason Schmidt | Jason Schmidt | Darren Oliver | Tim Worrell | 713 | 718 | -5 |
| 2003-08-27 | vs SFN | 135 | L 4-6 | 64-71 | 4 | 24,972 | Jose Jimenez | Sidney Ponson | Sidney Ponson | Jose Jimenez | Tim Worrell | 717 | 724 | -7 |
| 2003-08-28 | vs SFN | 136 | W 6-1 | 65-71 | 4 | 23,645 | Jason Jennings | Kevin Correia | Jason Jennings | Kevin Correia | | 723 | 725 | -2 |
| 2003-08-29 | @ LAN | 137 | L 4-6 | 65-72 | 4 | 39,092 | Cory Vance | Kevin Brown | Kevin Brown | Cory Vance | Eric Gagne | 727 | 731 | -4 |
| 2003-08-30 | @ LAN | 138 | L 0-5 | 65-73 | 4 | 35,136 | Denny Stark | Kazuhisa Ishii | Guillermo Mota | Denny Stark | | 727 | 736 | -9 |
| 2003-08-31 | @ LAN | 139 | L 0-3 | 65-74 | 4 | 41,146 | Darren Oliver | Odalis Perez | Odalis Perez | Darren Oliver | Eric Gagne | 727 | 739 | -12 |
| 2003-09-02 | @ SFN | 140 | L 1-2 | 65-75 | 4 | 39,419 | Jose Jimenez | Kevin Correia | Matt Herges | Adam Bernero | Tim Worrell | 728 | 741 | -13 |
| 2003-09-03 | @ SFN | 141 | L 6-7 | 65-76 | 4 | 38,490 | Jason Jennings | Kirk Rueter | Joe Nathan | Brian Fuentes | | 734 | 748 | -14 |
| 2003-09-05 | vs LAN | 142 | L 7-8 | 65-77 | 4 | 26,828 | Denny Stark | Kazuhisa Ishii | Guillermo Mota | Steve Reed | Eric Gagne | 741 | 756 | -15 |
| 2003-09-06 | vs LAN | 143 | L 2-10 | 65-78 | 4 | 24,393 | Darren Oliver | Odalis Perez | Odalis Perez | Darren Oliver | | 743 | 766 | -23 |
| 2003-09-07 | vs LAN | 144 | L 2-6 | 65-79 | 4 | 24,553 | Jose Jimenez | Wilson Alvarez | Wilson Alvarez | Jose Jimenez | Eric Gagne | 745 | 772 | -27 |
| 2003-09-09 | @ SLN | 145 | W 8-1 | 66-79 | 4 | 27,591 | Jason Jennings | Dan Haren | Jason Jennings | Dan Haren | | 753 | 773 | -20 |
| 2003-09-10 | @ SLN | 146 | L 2-10 | 66-80 | 4 | 25,396 | Scott Elarton | Brett Tomko | Brett Tomko | Scott Elarton | | 755 | 783 | -28 |
| 2003-09-11 | @ SLN | 147 | W 9-4 | 67-80 | 4 | 28,801 | Darren Oliver | Sterling Hitchcock | Darren Oliver | Sterling Hitchcock | | 764 | 787 | -23 |
| 2003-09-12 | @ ARI | 148 | W 8-2 | 68-80 | 4 | 32,922 | Jose Jimenez | Elmer Dessens | Jose Jimenez | Elmer Dessens | | 772 | 789 | -17 |
| 2003-09-13 | @ ARI | 149 | L 6-16 | 68-81 | 4 | 37,139 | Jason Young | Miguel Batista | Miguel Batista | Jason Young | | 778 | 805 | -27 |
| 2003-09-14 | @ ARI | 150 | L 0-5 | 68-82 | 4 | 35,153 | Jason Jennings | Randy Johnson | Randy Johnson | Jason Jennings | | 778 | 810 | -32 |
| 2003-09-16 | vs HOU | 151 | L 4-14 | 68-83 | 4 | 22,328 | Chin-hui Tsao | Jeriome Robertson | Jeriome Robertson | Chin-hui Tsao | | 782 | 824 | -42 |
| 2003-09-17 | vs HOU | 152 | W 7-5 | 69-83 | 4 | 22,454 | Darren Oliver | Ron Villone | Darren Oliver | Ron Villone | Justin Speier | 789 | 829 | -40 |
| 2003-09-18 | vs HOU | 153 | L 0-6 | 69-84 | 4 | 21,718 | Jose Jimenez | Wade Miller | Wade Miller | Jose Jimenez | | 789 | 835 | -46 |
| 2003-09-19 | vs SDN | 154 | W 6-5 | 70-84 | 4 | 31,976 | Scott Elarton | Ben Howard | Scott Elarton | Ben Howard | Brian Fuentes | 795 | 840 | -45 |
| 2003-09-20 | vs SDN | 155 | L 3-11 | 70-85 | 4 | 28,028 | Cory Vance | Brian Lawrence | Brian Lawrence | Cory Vance | | 798 | 851 | -53 |
| 2003-09-21 | vs SDN | 156 | W 5-3 | 71-85 | 4 | 28,167 | Chin-hui Tsao | Adam Eaton | Chin-hui Tsao | Adam Eaton | Brian Fuentes | 803 | 854 | -51 |
| 2003-09-23 | vs ARI | 157 | W 20-9 | 72-85 | 4 | 22,686 | Darren Oliver | Brandon Webb | Darren Oliver | Brandon Webb | | 823 | 863 | -40 |
| 2003-09-24 | vs ARI | 158 | L 3-6 | 72-86 | 4 | 24,465 | Jose Jimenez | Randy Johnson | Randy Johnson | Jose Jimenez | Matt Mantei | 826 | 869 | -43 |
| 2003-09-25 | vs ARI | 159 | L 7-8 | 72-87 | 4 | 23,056 | Scott Elarton | Miguel Batista | Oscar Villarreal | Brian Fuentes | Matt Mantei | 833 | 877 | -44 |
| 2003-09-26 | @ SDN | 160 | L 0-5 | 72-88 | 4 | 45,588 | Cory Vance | Adam Eaton | Adam Eaton | Cory Vance | | 833 | 882 | -49 |
| 2003-09-27 | @ SDN | 161 | W 10-2 | 73-88 | 4 | 42,479 | Denny Stark | Mike Bynum | Denny Stark | Mike Bynum | | 843 | 884 | -41 |
| 2003-09-28 | @ SDN | 162 | W 10-8 | 74-88 | 4 | 60,988 | Darren Oliver | Jake Peavy | Javier Lopez | Jay Witasick | Justin Speier | 853 | 892 | -39 |