| 2003-03-31 | @ FLO | 1 | W 8-5 | 1-0 | 2 | 37,137 | Kevin Millwood | Josh Beckett | Kevin Millwood | Josh Beckett | Jose Mesa | 8 | 5 | 3 |
| 2003-04-02 | @ FLO | 2 | W 8-2 | 2-0 | 2 | 10,534 | Randy Wolf | Carl Pavano | Randy Wolf | Carl Pavano | | 16 | 7 | 9 |
| 2003-04-03 | @ FLO | 3 | L 3-8 | 2-1 | 2 | 14,585 | Vicente Padilla | Mark Redman | Mark Redman | Vicente Padilla | | 19 | 15 | 4 |
| 2003-04-04 | vs PIT | 4 | L 1-9 | 2-2 | 3 | 59,269 | Joe Roa | Jeff Suppan | Jeff Suppan | Joe Roa | Salomon Torres | 20 | 24 | -4 |
| 2003-04-05 | vs PIT | 5 | W 16-1 | 3-2 | 3 | 22,693 | Kevin Millwood | Jeff D'Amico | Carlos Silva | Jeff D'Amico | | 36 | 25 | 11 |
| 2003-04-06 | vs PIT | 6 | L 0-2 | 3-3 | 3 | 30,113 | Brett Myers | Kris Benson | Kris Benson | Brett Myers | Mike Williams | 36 | 27 | 9 |
| 2003-04-08 | vs ATL | 7 | W 4-3 | 4-3 | 3 | 13,283 | Randy Wolf | Jason Marquis | Jose Mesa | Kevin Gryboski | | 40 | 30 | 10 |
| 2003-04-09 | vs ATL | 8 | W 16-2 | 5-3 | 1 | 14,724 | Vicente Padilla | Greg Maddux | Vicente Padilla | Greg Maddux | | 56 | 32 | 24 |
| 2003-04-10 | vs ATL | 9 | L 2-6 | 5-4 | 2 | 14,840 | Joe Roa | Trey Hodges | Darren Holmes | Joe Roa | | 58 | 38 | 20 |
| 2003-04-11 | @ CIN | 10 | L 6-7 | 5-5 | 2 | 27,738 | Brett Myers | Paul Wilson | Scott Williamson | Jose Mesa | | 64 | 45 | 19 |
| 2003-04-12 | @ CIN | 11 | W 8-5 | 6-5 | 2 | 28,598 | Kevin Millwood | Jimmy Haynes | Kevin Millwood | Jimmy Haynes | | 72 | 50 | 22 |
| 2003-04-13 | @ CIN | 12 | W 13-1 | 7-5 | 2 | 24,535 | Randy Wolf | Ryan Dempster | Randy Wolf | Ryan Dempster | | 85 | 51 | 34 |
| 2003-04-14 | vs FLO | 13 | W 5-2 | 8-5 | 2 | 13,611 | Vicente Padilla | A.J. Burnett | Vicente Padilla | A.J. Burnett | Jose Mesa | 90 | 53 | 37 |
| 2003-04-15 | vs FLO | 14 | W 4-3 | 9-5 | 2 | 17,508 | Joe Roa | Josh Beckett | Carlos Silva | Josh Beckett | Jose Mesa | 94 | 56 | 38 |
| 2003-04-16 | vs FLO | 15 | L 1-3 | 9-6 | 2 | 15,167 | Brett Myers | Brad Penny | Brad Penny | Brett Myers | Braden Looper | 95 | 59 | 36 |
| 2003-04-17 | vs FLO | 16 | L 3-7 | 9-7 | 2 | 13,968 | Kevin Millwood | Carl Pavano | Carl Pavano | Kevin Millwood | | 98 | 66 | 32 |
| 2003-04-18 | @ ATL | 17 | L 4-5 | 9-8 | 3 | 28,100 | Randy Wolf | Greg Maddux | Kevin Gryboski | Randy Wolf | John Smoltz | 102 | 71 | 31 |
| 2003-04-19 | @ ATL | 18 | W 4-0 | 10-8 | 2 | 29,777 | Vicente Padilla | Mike Hampton | Vicente Padilla | Mike Hampton | | 106 | 71 | 35 |
| 2003-04-20 | @ ATL | 19 | L 1-8 | 10-9 | 3 | 22,978 | Brandon Duckworth | Shane Reynolds | Shane Reynolds | Brandon Duckworth | | 107 | 79 | 28 |
| 2003-04-22 | vs COL | 20 | W 5-2 | 11-9 | 3 | 13,431 | Kevin Millwood | Darren Oliver | Kevin Millwood | Darren Oliver | Jose Mesa | 112 | 81 | 31 |
| 2003-04-23 | vs COL | 21 | W 6-4 | 12-9 | 3 | 13,444 | Brett Myers | Jason Jennings | Brett Myers | Jason Jennings | Jose Mesa | 118 | 85 | 33 |
| 2003-04-24 | vs COL | 22 | W 9-1 | 13-9 | 3 | 16,947 | Randy Wolf | Aaron Cook | Randy Wolf | Aaron Cook | | 127 | 86 | 41 |
| 2003-04-25 | vs SFN | 23 | L 4-7 | 13-10 | 3 | 20,650 | Vicente Padilla | Kurt Ainsworth | Joe Nathan | Vicente Padilla | | 131 | 93 | 38 |
| 2003-04-26 | vs SFN | 24 | W 10-2 | 14-10 | 3 | 19,464 | Brandon Duckworth | Jerome Williams | Brandon Duckworth | Jerome Williams | Carlos Silva | 141 | 95 | 46 |
| 2003-04-27 | vs SFN | 25 | W 1-0 | 15-10 | 3 | 40,016 | Kevin Millwood | Jesse Foppert | Kevin Millwood | Jesse Foppert | | 142 | 95 | 47 |
| 2003-04-28 | @ LAN | 26 | W 3-0 | 16-10 | 1 | 24,241 | Brett Myers | Darren Dreifort | Brett Myers | Darren Dreifort | Jose Mesa | 145 | 95 | 50 |
| 2003-04-29 | @ LAN | 27 | L 2-6 | 16-11 | 3 | 27,815 | Randy Wolf | Kevin Brown | Kevin Brown | Randy Wolf | | 147 | 101 | 46 |
| 2003-04-30 | @ LAN | 28 | L 0-4 | 16-12 | 3 | 24,940 | Vicente Padilla | Odalis Perez | Odalis Perez | Vicente Padilla | Eric Gagne | 147 | 105 | 42 |
| 2003-05-01 | @ LAN | 29 | W 4-1 | 17-12 | 3 | 24,008 | Brandon Duckworth | Hideo Nomo | Brandon Duckworth | Hideo Nomo | Jose Mesa | 151 | 106 | 45 |
| 2003-05-02 | @ SDN | 30 | L 4-5 | 17-13 | 3 | 20,595 | Kevin Millwood | Clay Condrey | Mike Matthews | Jose Mesa | | 155 | 111 | 44 |
| 2003-05-03 | @ SDN | 31 | W 5-4 | 18-13 | 3 | 29,725 | Brett Myers | Brian Lawrence | Carlos Silva | Jaret Wright | Jose Mesa | 160 | 115 | 45 |
| 2003-05-04 | @ SDN | 32 | W 3-1 | 19-13 | 2 | 21,526 | Randy Wolf | Adam Eaton | Randy Wolf | Adam Eaton | Jose Mesa | 163 | 116 | 47 |
| 2003-05-05 | @ ARI | 33 | L 1-10 | 19-14 | 3 | 25,407 | Vicente Padilla | Miguel Batista | Miguel Batista | Vicente Padilla | | 164 | 126 | 38 |
| 2003-05-06 | @ ARI | 34 | L 5-6 | 19-15 | 3 | 32,151 | Brandon Duckworth | Andrew Good | Oscar Villarreal | Terry Adams | | 169 | 132 | 37 |
| 2003-05-07 | @ ARI | 35 | W 5-2 | 20-15 | 3 | 28,485 | Kevin Millwood | Brandon Webb | Kevin Millwood | Brandon Webb | Jose Mesa | 174 | 134 | 40 |
| 2003-05-09 | vs HOU | 36 | W 5-3 | 21-15 | 3 | 20,109 | Brett Myers | Roy Oswalt | Brett Myers | Roy Oswalt | Jose Mesa | 179 | 137 | 42 |
| 2003-05-10 | vs HOU | 37 | W 2-0 | 22-15 | 3 | 20,726 | Randy Wolf | Wade Miller | Randy Wolf | Wade Miller | | 181 | 137 | 44 |
| 2003-05-11 | vs HOU | 38 | L 7-10 | 22-16 | 3 | 29,054 | Vicente Padilla | Kirk Saarloos | Peter Munro | Vicente Padilla | Billy Wagner | 188 | 147 | 41 |
| 2003-05-13 | vs ARI | 39 | L 1-6 | 22-17 | 3 | 19,016 | Kevin Millwood | Brandon Webb | Mike Koplove | Jose Mesa | | 189 | 153 | 36 |
| 2003-05-14 | vs ARI | 40 | L 0-2 | 22-18 | 3 | 19,195 | Brett Myers | Curt Schilling | Curt Schilling | Brett Myers | | 189 | 155 | 34 |
| 2003-05-15 | vs ARI | 41 | W 6-4 | 23-18 | 3 | 24,012 | Randy Wolf | Elmer Dessens | Rheal Cormier | Oscar Villarreal | Jose Mesa | 195 | 159 | 36 |
| 2003-05-16 | @ HOU | 42 | L 2-4 | 23-19 | 3 | 28,085 | Vicente Padilla | Jeriome Robertson | Octavio Dotel | Turk Wendell | Billy Wagner | 197 | 163 | 34 |
| 2003-05-17 | @ HOU | 43 | W 9-4 | 24-19 | 3 | 30,289 | Brandon Duckworth | Scott Linebrink | Brandon Duckworth | Nate Bland | | 206 | 167 | 39 |
| 2003-05-18 | @ HOU | 44 | W 3-1 | 25-19 | 3 | 28,585 | Kevin Millwood | Tim Redding | Kevin Millwood | Tim Redding | | 209 | 168 | 41 |
| 2003-05-20 | @ NYN | 45 | W 11-7 | 26-19 | 3 | 25,281 | Brett Myers | Jae Weong Seo | Brett Myers | Graeme Lloyd | | 220 | 175 | 45 |
| 2003-05-21 | @ NYN | 46 | L 4-5 | 26-20 | 3 | 29,551 | Randy Wolf | Al Leiter | Armando Benitez | Terry Adams | | 224 | 180 | 44 |
| 2003-05-22 | @ NYN | 47 | L 3-6 | 26-21 | 3 | 20,101 | Vicente Padilla | Pedro Astacio | Pedro Astacio | Vicente Padilla | Armando Benitez | 227 | 186 | 41 |
| 2003-05-23 | @ MON | 48 | W 4-2 | 27-21 | 3 | 9,511 | Kevin Millwood | Zach Day | Kevin Millwood | Zach Day | Jose Mesa | 231 | 188 | 43 |
| 2003-05-24 | @ MON | 49 | L 2-3 | 27-22 | 3 | 33,236 | Brandon Duckworth | Tomo Ohka | Luis Ayala | Carlos Silva | | 233 | 191 | 42 |
| 2003-05-25 | @ MON | 50 | L 3-5 | 27-23 | 3 | 17,023 | Brett Myers | Javier Vazquez | Javier Vazquez | Brett Myers | Rocky Biddle | 236 | 196 | 40 |
| 2003-05-27 | vs NYN | 51 | L 2-4 | 27-24 | 3 | 18,081 | Randy Wolf | Al Leiter | Al Leiter | Randy Wolf | Armando Benitez | 238 | 200 | 38 |
| 2003-05-28 | vs NYN | 52 | W 11-3 | 28-24 | 3 | 21,389 | Vicente Padilla | Pedro Astacio | Vicente Padilla | Pedro Astacio | | 249 | 203 | 46 |
| 2003-05-29 | vs NYN | 53 | L 0-5 | 28-25 | 3 | 19,568 | Kevin Millwood | Steve Trachsel | Steve Trachsel | Kevin Millwood | | 249 | 208 | 41 |
| 2003-05-30 | vs MON | 54 | W 12-5 | 29-25 | 3 | 18,311 | Brandon Duckworth | Javier Vazquez | Rheal Cormier | Javier Vazquez | | 261 | 213 | 48 |
| 2003-06-01 | vs MON | 55 | W 4-3 | 31-25 | 3 | 0 | Randy Wolf | Livan Hernandez | Randy Wolf | Livan Hernandez | Jose Mesa | 265 | 216 | 49 |
| 2003-06-01 | vs MON | 56 | W 4-1 | 31-25 | 3 | 36,685 | Brett Myers | Claudio Vargas | Brett Myers | Dan Smith | Jose Mesa | 269 | 217 | 52 |
| 2003-06-03 | vs SEA | 57 | L 0-4 | 31-26 | 3 | 18,029 | Kevin Millwood | Jamie Moyer | Jamie Moyer | Kevin Millwood | | 269 | 221 | 48 |
| 2003-06-04 | vs SEA | 58 | L 2-7 | 31-27 | 3 | 16,232 | Vicente Padilla | Gil Meche | Gil Meche | Vicente Padilla | | 271 | 228 | 43 |
| 2003-06-05 | vs SEA | 59 | L 4-5 | 31-28 | 3 | 21,145 | Brandon Duckworth | Joel Pineiro | Julio Mateo | Jose Mesa | Kazuhiro Sasaki | 275 | 233 | 42 |
| 2003-06-06 | vs OAK | 60 | L 4-7 | 31-29 | 3 | 29,583 | Brett Myers | Barry Zito | Barry Zito | Brett Myers | | 279 | 240 | 39 |
| 2003-06-08 | vs OAK | 61 | W 7-1 | 33-29 | 3 | 0 | Kevin Millwood | Mark Mulder | Kevin Millwood | Mark Mulder | | 286 | 241 | 45 |
| 2003-06-08 | vs OAK | 62 | W 8-3 | 33-29 | 3 | 37,662 | Randy Wolf | Aaron Harang | Randy Wolf | Aaron Harang | | 294 | 244 | 50 |
| 2003-06-09 | @ ANA | 63 | W 3-0 | 34-29 | 3 | 25,902 | Vicente Padilla | Jarrod Washburn | Vicente Padilla | Jarrod Washburn | Jose Mesa | 297 | 244 | 53 |
| 2003-06-10 | @ ANA | 64 | L 1-2 | 34-30 | 3 | 34,037 | Brandon Duckworth | John Lackey | John Lackey | Brandon Duckworth | Troy Percival | 298 | 246 | 52 |
| 2003-06-11 | @ ANA | 65 | L 3-5 | 34-31 | 3 | 31,130 | Brett Myers | Kevin Appier | Ben Weber | Brett Myers | Troy Percival | 301 | 251 | 50 |
| 2003-06-13 | @ CIN | 66 | L 1-15 | 34-32 | 3 | 30,144 | Kevin Millwood | Jimmy Haynes | Jimmy Haynes | Kevin Millwood | | 302 | 266 | 36 |
| 2003-06-14 | @ CIN | 67 | W 12-2 | 35-32 | 3 | 35,398 | Randy Wolf | Danny Graves | Randy Wolf | Danny Graves | | 314 | 268 | 46 |
| 2003-06-17 | vs ATL | 68 | W 5-4 | 36-32 | 3 | 24,133 | Brett Myers | Shane Reynolds | Turk Wendell | Darren Holmes | | 319 | 272 | 47 |
| 2003-06-18 | vs ATL | 69 | L 1-6 | 36-33 | 3 | 26,475 | Kevin Millwood | Russ Ortiz | Russ Ortiz | Kevin Millwood | | 320 | 278 | 42 |
| 2003-06-19 | vs ATL | 70 | W 3-2 | 37-33 | 3 | 27,207 | Vicente Padilla | Mike Hampton | Jose Mesa | John Smoltz | | 323 | 280 | 43 |
| 2003-06-21 | vs BOS | 71 | W 6-5 | 38-33 | 3 | 35,512 | Randy Wolf | Pedro Martinez | Jose Mesa | Rudy Seanez | | 329 | 285 | 44 |
| 2003-06-22 | vs BOS | 72 | W 5-0 | 39-33 | 3 | 60,960 | Brett Myers | Byung-Hyun Kim | Brett Myers | Byung-Hyun Kim | | 334 | 285 | 49 |
| 2003-06-24 | @ ATL | 73 | L 3-5 | 39-34 | 3 | 31,796 | Kevin Millwood | Russ Ortiz | Russ Ortiz | Kevin Millwood | John Smoltz | 337 | 290 | 47 |
| 2003-06-25 | @ ATL | 74 | W 8-1 | 40-34 | 3 | 31,724 | Vicente Padilla | Greg Maddux | Vicente Padilla | Greg Maddux | | 345 | 291 | 54 |
| 2003-06-26 | @ ATL | 75 | W 8-1 | 41-34 | 3 | 30,405 | Randy Wolf | Mike Hampton | Randy Wolf | Mike Hampton | | 353 | 292 | 61 |
| 2003-06-27 | @ BAL | 76 | W 4-2 | 42-34 | 2 | 46,405 | Brandon Duckworth | Jason Johnson | Dan Plesac | Omar Daal | Hector Mercado | 357 | 294 | 63 |
| 2003-06-28 | @ BAL | 77 | W 9-5 | 43-34 | 2 | 49,549 | Brett Myers | Pat Hentgen | Brett Myers | Pat Hentgen | | 366 | 299 | 67 |
| 2003-06-29 | @ BAL | 78 | W 4-3 | 44-34 | 2 | 44,723 | Kevin Millwood | Rick Helling | Kevin Millwood | Rick Helling | Jose Mesa | 370 | 302 | 68 |
| 2003-06-30 | vs CHN | 79 | W 4-3 | 45-34 | 2 | 23,323 | Vicente Padilla | Shawn Estes | Vicente Padilla | Shawn Estes | Jose Mesa | 374 | 305 | 69 |
| 2003-07-01 | vs CHN | 80 | W 4-3 | 46-34 | 2 | 25,307 | Randy Wolf | Mark Prior | Terry Adams | Mike Remlinger | | 378 | 308 | 70 |
| 2003-07-02 | vs CHN | 81 | L 0-1 | 46-35 | 2 | 23,591 | Brandon Duckworth | Matt Clement | Kyle Farnsworth | Turk Wendell | Joe Borowski | 378 | 309 | 69 |
| 2003-07-03 | vs CHN | 82 | W 12-2 | 47-35 | 2 | 57,326 | Brett Myers | Carlos Zambrano | Brett Myers | Carlos Zambrano | | 390 | 311 | 79 |
| 2003-07-04 | vs FLO | 83 | L 1-2 | 47-36 | 2 | 19,690 | Kevin Millwood | Carl Pavano | Braden Looper | Jose Mesa | | 391 | 313 | 78 |
| 2003-07-05 | vs FLO | 84 | L 4-5 | 47-37 | 2 | 52,110 | Vicente Padilla | Brad Penny | Brad Penny | Vicente Padilla | Braden Looper | 395 | 318 | 77 |
| 2003-07-06 | vs FLO | 85 | L 3-6 | 47-38 | 2 | 26,244 | Randy Wolf | Mark Redman | Mark Redman | Randy Wolf | | 398 | 324 | 74 |
| 2003-07-07 | @ MON | 86 | L 1-8 | 47-39 | 2 | 7,099 | Brandon Duckworth | Livan Hernandez | Livan Hernandez | Brandon Duckworth | | 399 | 332 | 67 |
| 2003-07-08 | @ MON | 87 | W 13-6 | 48-39 | 2 | 8,225 | Brett Myers | Claudio Vargas | Brett Myers | Claudio Vargas | | 412 | 338 | 74 |
| 2003-07-09 | @ MON | 88 | W 2-0 | 49-39 | 2 | 7,005 | Kevin Millwood | Tomo Ohka | Kevin Millwood | Tomo Ohka | | 414 | 338 | 76 |
| 2003-07-10 | @ NYN | 89 | W 7-2 | 50-39 | 2 | 25,913 | Vicente Padilla | Steve Trachsel | Vicente Padilla | Steve Trachsel | | 421 | 340 | 81 |
| 2003-07-11 | @ NYN | 90 | W 10-3 | 51-39 | 2 | 35,884 | Randy Wolf | Aaron Heilman | Randy Wolf | Aaron Heilman | | 431 | 343 | 88 |
| 2003-07-12 | @ NYN | 91 | W 4-2 | 52-39 | 2 | 33,452 | Brandon Duckworth | Jae Weong Seo | Jose Mesa | John Franco | | 435 | 345 | 90 |
| 2003-07-13 | @ NYN | 92 | L 3-4 | 52-40 | 2 | 31,630 | Brett Myers | Tom Glavine | Armando Benitez | Terry Adams | | 438 | 349 | 89 |
| 2003-07-17 | vs MON | 93 | W 5-2 | 53-40 | 2 | 23,874 | Kevin Millwood | Tomo Ohka | Dan Plesac | Tim Drew | | 443 | 351 | 92 |
| 2003-07-18 | vs MON | 94 | L 1-3 | 53-41 | 2 | 22,789 | Randy Wolf | Javier Vazquez | Javier Vazquez | Randy Wolf | | 444 | 354 | 90 |
| 2003-07-19 | vs MON | 95 | W 4-3 | 54-41 | 2 | 28,794 | Vicente Padilla | Livan Hernandez | Jose Mesa | Hector Almonte | | 448 | 357 | 91 |
| 2003-07-20 | vs MON | 96 | W 3-2 | 55-41 | 2 | 37,552 | Brett Myers | Claudio Vargas | Brett Myers | Claudio Vargas | Jose Mesa | 451 | 359 | 92 |
| 2003-07-21 | vs NYN | 97 | L 6-8 | 55-42 | 2 | 33,208 | Brandon Duckworth | Aaron Heilman | Aaron Heilman | Brandon Duckworth | John Franco | 457 | 367 | 90 |
| 2003-07-22 | vs NYN | 98 | L 5-7 | 55-43 | 2 | 37,164 | Kevin Millwood | Steve Trachsel | Steve Trachsel | Kevin Millwood | Dan Wheeler | 462 | 374 | 88 |
| 2003-07-23 | @ CHN | 99 | W 3-0 | 56-43 | 2 | 40,377 | Randy Wolf | Matt Clement | Randy Wolf | Matt Clement | | 465 | 374 | 91 |
| 2003-07-24 | @ CHN | 100 | W 14-6 | 57-43 | 2 | 40,266 | Vicente Padilla | Kerry Wood | Vicente Padilla | Kerry Wood | | 479 | 380 | 99 |
| 2003-07-25 | @ FLO | 101 | L 5-11 | 57-44 | 2 | 18,106 | Brett Myers | Dontrelle Willis | Ugueth Urbina | Mike Williams | | 484 | 391 | 93 |
| 2003-07-26 | @ FLO | 102 | L 5-10 | 57-45 | 2 | 20,545 | Brandon Duckworth | Josh Beckett | Josh Beckett | Brandon Duckworth | Braden Looper | 489 | 401 | 88 |
| 2003-07-27 | @ FLO | 103 | L 6-7 | 57-46 | 2 | 12,467 | Kevin Millwood | Carl Pavano | Ugueth Urbina | Mike Williams | | 495 | 408 | 87 |
| 2003-07-28 | @ CIN | 104 | L 5-6 | 57-47 | 2 | 29,200 | Randy Wolf | Ryan Dempster | Scott Williamson | Terry Adams | | 500 | 414 | 86 |
| 2003-07-29 | vs LAN | 105 | W 2-0 | 58-47 | 2 | 31,099 | Vicente Padilla | Kazuhisa Ishii | Vicente Padilla | Kazuhisa Ishii | Jose Mesa | 502 | 414 | 88 |
| 2003-07-30 | vs LAN | 106 | W 4-2 | 59-47 | 2 | 26,580 | Brett Myers | Kevin Brown | Turk Wendell | Paul Shuey | Jose Mesa | 506 | 416 | 90 |
| 2003-07-31 | vs LAN | 107 | W 7-3 | 60-47 | 2 | 24,932 | Brandon Duckworth | Odalis Perez | Brandon Duckworth | Odalis Perez | | 513 | 419 | 94 |
| 2003-08-01 | vs SDN | 108 | W 6-0 | 61-47 | 2 | 18,655 | Kevin Millwood | Kevin Jarvis | Kevin Millwood | Kevin Jarvis | | 519 | 419 | 100 |
| 2003-08-02 | vs SDN | 109 | L 4-6 | 62-48 | 2 | 0 | Randy Wolf | Jake Peavy | Jake Peavy | Randy Wolf | | 523 | 425 | 98 |
| 2003-08-02 | vs SDN | 110 | W 10-4 | 62-48 | 2 | 35,239 | Carlos Silva | Joe Roa | Rheal Cormier | Joe Roa | | 533 | 429 | 104 |
| 2003-08-03 | vs SDN | 111 | L 2-5 | 62-49 | 2 | 43,839 | Vicente Padilla | Oliver Perez | Jay Witasick | Jose Mesa | Rod Beck | 535 | 434 | 101 |
| 2003-08-05 | @ COL | 112 | W 7-2 | 63-49 | 2 | 28,034 | Brett Myers | Shawn Chacon | Brett Myers | Shawn Chacon | | 542 | 436 | 106 |
| 2003-08-06 | @ COL | 113 | L 1-5 | 63-50 | 2 | 27,599 | Brandon Duckworth | Chin-hui Tsao | Chin-hui Tsao | Brandon Duckworth | | 543 | 441 | 102 |
| 2003-08-07 | @ COL | 114 | L 3-4 | 63-51 | 2 | 27,855 | Kevin Millwood | Denny Stark | Javier Lopez | Kevin Millwood | Justin Speier | 546 | 445 | 101 |
| 2003-08-08 | @ SFN | 115 | L 1-9 | 63-52 | 3 | 42,595 | Randy Wolf | Jesse Foppert | Jesse Foppert | Randy Wolf | | 547 | 454 | 93 |
| 2003-08-09 | @ SFN | 116 | W 8-6 | 64-52 | 3 | 42,572 | Vicente Padilla | Dustin Hermanson | Turk Wendell | Jim Brower | | 555 | 460 | 95 |
| 2003-08-10 | @ SFN | 117 | L 2-5 | 64-53 | 3 | 42,520 | Brett Myers | Kevin Correia | Kevin Correia | Brett Myers | | 557 | 465 | 92 |
| 2003-08-12 | vs MIL | 118 | L 3-6 | 64-54 | 3 | 23,136 | Brandon Duckworth | Wayne Franklin | Wayne Franklin | Brandon Duckworth | Danny Kolb | 560 | 471 | 89 |
| 2003-08-13 | vs MIL | 119 | W 11-4 | 65-54 | 3 | 24,683 | Kevin Millwood | Ben Sheets | Kevin Millwood | Ben Sheets | | 571 | 475 | 96 |
| 2003-08-14 | vs MIL | 120 | W 4-3 | 66-54 | 2 | 23,394 | Randy Wolf | Wes Obermueller | Randy Wolf | Wes Obermueller | Mike Williams | 575 | 478 | 97 |
| 2003-08-15 | vs SLN | 121 | W 7-4 | 67-54 | 2 | 28,962 | Vicente Padilla | Woody Williams | Vicente Padilla | Woody Williams | Dan Plesac | 582 | 482 | 100 |
| 2003-08-16 | vs SLN | 122 | W 5-4 | 68-54 | 2 | 35,046 | Brett Myers | Dan Haren | Brett Myers | Dan Haren | Jose Mesa | 587 | 486 | 101 |
| 2003-08-17 | vs SLN | 123 | W 6-4 | 69-54 | 2 | 42,153 | Amaury Telemaco | Brett Tomko | Amaury Telemaco | Brett Tomko | Mike Williams | 593 | 490 | 103 |
| 2003-08-19 | @ MIL | 124 | L 4-6 | 69-55 | 2 | 17,028 | Kevin Millwood | Ben Sheets | Mike DeJean | Turk Wendell | Danny Kolb | 597 | 496 | 101 |
| 2003-08-20 | @ MIL | 125 | L 1-10 | 69-56 | 2 | 18,115 | Randy Wolf | Matt Kinney | Matt Kinney | Randy Wolf | | 598 | 506 | 92 |
| 2003-08-21 | @ MIL | 126 | L 2-5 | 69-57 | 2 | 19,885 | Vicente Padilla | Doug Davis | Leo Estrella | Vicente Padilla | Danny Kolb | 600 | 511 | 89 |
| 2003-08-22 | @ SLN | 127 | W 9-4 | 70-57 | 2 | 33,824 | Brett Myers | Dan Haren | Rheal Cormier | Steve Kline | | 609 | 515 | 94 |
| 2003-08-23 | @ SLN | 128 | L 3-5 | 70-58 | 2 | 37,318 | Amaury Telemaco | Matt Morris | Sterling Hitchcock | Amaury Telemaco | Jason Isringhausen | 612 | 520 | 92 |
| 2003-08-24 | @ SLN | 129 | L 0-3 | 70-59 | 2 | 37,679 | Kevin Millwood | Brett Tomko | Brett Tomko | Kevin Millwood | Mike DeJean | 612 | 523 | 89 |
| 2003-08-25 | @ MON | 130 | L 1-12 | 70-60 | 3 | 30,501 | Randy Wolf | Livan Hernandez | Livan Hernandez | Randy Wolf | | 613 | 535 | 78 |
| 2003-08-26 | @ MON | 131 | L 10-14 | 70-61 | 3 | 12,509 | Vicente Padilla | Zach Day | Joey Eischen | Mike Williams | Luis Ayala | 623 | 549 | 74 |
| 2003-08-27 | @ MON | 132 | L 6-9 | 70-62 | 3 | 20,105 | Brett Myers | Tomo Ohka | Hector Almonte | Dan Plesac | Rocky Biddle | 629 | 558 | 71 |
| 2003-08-28 | @ MON | 133 | L 0-4 | 70-63 | 3 | 20,030 | Amaury Telemaco | Javier Vazquez | Javier Vazquez | Amaury Telemaco | | 629 | 562 | 67 |
| 2003-08-29 | @ NYN | 134 | W 7-0 | 71-63 | 3 | 33,208 | Kevin Millwood | Steve Trachsel | Kevin Millwood | Steve Trachsel | | 636 | 562 | 74 |
| 2003-08-30 | @ NYN | 135 | W 4-2 | 72-63 | 3 | 26,769 | Randy Wolf | Tom Glavine | Randy Wolf | Tom Glavine | Jose Mesa | 640 | 564 | 76 |
| 2003-08-31 | @ NYN | 136 | W 4-1 | 73-63 | 3 | 26,180 | Vicente Padilla | Jae Weong Seo | Vicente Padilla | Jae Weong Seo | Jose Mesa | 644 | 565 | 79 |
| 2003-09-01 | vs BOS | 137 | L 9-13 | 73-64 | 3 | 61,068 | Brett Myers | Jeff Suppan | Byung-Hyun Kim | Jose Mesa | | 653 | 578 | 75 |
| 2003-09-02 | vs MON | 138 | W 5-3 | 74-64 | 3 | 26,719 | Amaury Telemaco | Javier Vazquez | Rheal Cormier | Javier Vazquez | Dan Plesac | 658 | 581 | 77 |
| 2003-09-03 | vs MON | 139 | W 8-3 | 75-64 | 3 | 18,002 | Kevin Millwood | T.J. Tucker | Kevin Millwood | T.J. Tucker | | 666 | 584 | 82 |
| 2003-09-04 | vs NYN | 140 | W 6-5 | 76-64 | 3 | 19,259 | Randy Wolf | Tom Glavine | Valerio de los Santos | Mike Stanton | | 672 | 589 | 83 |
| 2003-09-05 | vs NYN | 141 | W 1-0 | 77-64 | 2 | 26,712 | Vicente Padilla | Jae Weong Seo | Vicente Padilla | Jae Weong Seo | Rheal Cormier | 673 | 589 | 84 |
| 2003-09-06 | vs NYN | 142 | W 9-6 | 78-64 | 2 | 38,671 | Brett Myers | Jeremy Griffiths | Brett Myers | Jeremy Griffiths | Turk Wendell | 682 | 595 | 87 |
| 2003-09-07 | vs NYN | 143 | W 5-4 | 79-64 | 2 | 29,159 | Amaury Telemaco | Al Leiter | Rheal Cormier | Dan Wheeler | | 687 | 599 | 88 |
| 2003-09-08 | @ ATL | 144 | L 4-6 | 79-65 | 3 | 17,543 | Kevin Millwood | Russ Ortiz | Russ Ortiz | Kevin Millwood | Will Cunnane | 691 | 605 | 86 |
| 2003-09-09 | @ ATL | 145 | W 18-5 | 80-65 | 3 | 21,257 | Randy Wolf | Shane Reynolds | Randy Wolf | Shane Reynolds | | 709 | 610 | 99 |
| 2003-09-10 | @ ATL | 146 | L 2-4 | 80-66 | 3 | 21,321 | Vicente Padilla | Horacio Ramirez | Horacio Ramirez | Vicente Padilla | Will Cunnane | 711 | 614 | 97 |
| 2003-09-11 | @ ATL | 147 | W 8-3 | 81-66 | 3 | 23,811 | Brett Myers | Greg Maddux | Brett Myers | Greg Maddux | | 719 | 617 | 102 |
| 2003-09-12 | @ PIT | 148 | L 4-8 | 81-67 | 3 | 18,895 | Amaury Telemaco | Kip Wells | Kip Wells | Amaury Telemaco | | 723 | 625 | 98 |
| 2003-09-13 | @ PIT | 149 | L 3-5 | 81-68 | 3 | 33,480 | Kevin Millwood | Josh Fogg | Josh Fogg | Kevin Millwood | Julian Tavarez | 726 | 630 | 96 |
| 2003-09-14 | @ PIT | 150 | W 10-7 | 82-68 | 3 | 16,383 | Randy Wolf | Salomon Torres | Randy Wolf | Salomon Torres | Mike Williams | 736 | 637 | 99 |
| 2003-09-16 | vs FLO | 151 | W 14-0 | 83-68 | 3 | 36,479 | Vicente Padilla | Carl Pavano | Vicente Padilla | Carl Pavano | | 750 | 637 | 113 |
| 2003-09-17 | vs FLO | 152 | L 4-11 | 83-69 | 3 | 33,761 | Brett Myers | Mark Redman | Mark Redman | Brett Myers | | 754 | 648 | 106 |
| 2003-09-18 | vs FLO | 153 | W 5-4 | 84-69 | 3 | 20,950 | Kevin Millwood | Dontrelle Willis | Rheal Cormier | Chad Fox | | 759 | 652 | 107 |
| 2003-09-19 | vs CIN | 154 | W 7-3 | 85-69 | 2 | 30,191 | Randy Wolf | Josh Hall | Randy Wolf | Josh Hall | | 766 | 655 | 111 |
| 2003-09-20 | vs CIN | 155 | L 0-2 | 85-70 | 3 | 35,239 | Amaury Telemaco | Todd Van Poppel | Todd Van Poppel | Amaury Telemaco | Chris Reitsma | 766 | 657 | 109 |
| 2003-09-21 | vs CIN | 156 | L 3-4 | 85-71 | 3 | 57,883 | Vicente Padilla | Aaron Harang | Dan Serafini | Vicente Padilla | Chris Reitsma | 769 | 661 | 108 |
| 2003-09-23 | @ FLO | 157 | L 4-5 | 85-72 | 3 | 25,311 | Kevin Millwood | Dontrelle Willis | Michael Tejera | Mike Williams | Ugueth Urbina | 773 | 666 | 107 |
| 2003-09-24 | @ FLO | 158 | L 5-6 | 85-73 | 3 | 28,520 | Brett Myers | Josh Beckett | Josh Beckett | Brett Myers | Ugueth Urbina | 778 | 672 | 106 |
| 2003-09-25 | @ FLO | 159 | L 4-8 | 85-74 | 3 | 31,935 | Randy Wolf | Brad Penny | Brad Penny | Randy Wolf | | 782 | 680 | 102 |
| 2003-09-26 | vs ATL | 160 | L 0-6 | 85-75 | 3 | 58,096 | Vicente Padilla | Horacio Ramirez | Horacio Ramirez | Vicente Padilla | | 782 | 686 | 96 |
| 2003-09-27 | vs ATL | 161 | W 7-6 | 86-75 | 3 | 58,303 | Amaury Telemaco | Mike Hampton | Rheal Cormier | Ray King | | 789 | 692 | 97 |
| 2003-09-28 | vs ATL | 162 | L 2-5 | 86-76 | 3 | 58,554 | Kevin Millwood | Greg Maddux | Greg Maddux | Kevin Millwood | Jason Marquis | 791 | 697 | 94 |