| 1988-04-04 | @ CHA | 1 | L 5-8 | 0-1 | 7 | 35,899 | Mike Witt | Ricky Horton | Ricky Horton | Mike Witt | Bobby Thigpen | 5 | 8 | -3 |
| 1988-04-06 | @ CHA | 2 | W 4-2 | 1-1 | 4 | 7,107 | Dan Petry | Jack McDowell | Donnie Moore | Bobby Thigpen | | 9 | 10 | -1 |
| 1988-04-07 | @ CHA | 3 | L 1-2 | 1-2 | 6 | 8,206 | Chuck Finley | Dave LaPoint | Dave LaPoint | Chuck Finley | Bill Long | 10 | 12 | -2 |
| 1988-04-08 | vs OAK | 4 | L 2-8 | 1-3 | 7 | 45,586 | Kirk McCaskill | Storm Davis | Storm Davis | Kirk McCaskill | Eric Plunk | 12 | 20 | -8 |
| 1988-04-09 | vs OAK | 5 | L 6-8 | 1-4 | 7 | 44,314 | Mike Witt | Dave Stewart | Dave Stewart | Donnie Moore | Dennis Eckersley | 18 | 28 | -10 |
| 1988-04-10 | vs OAK | 6 | W 6-4 | 2-4 | 7 | 31,297 | Willie Fraser | Bob Welch | Willie Fraser | Bob Welch | DeWayne Buice | 24 | 32 | -8 |
| 1988-04-12 | vs CHA | 7 | W 15-6 | 3-4 | 6 | 23,149 | Dan Petry | Jack McDowell | Dan Petry | Jack McDowell | | 39 | 38 | 1 |
| 1988-04-13 | vs CHA | 8 | W 5-2 | 4-4 | 4 | 22,765 | Chuck Finley | Dave LaPoint | Chuck Finley | Dave LaPoint | DeWayne Buice | 44 | 40 | 4 |
| 1988-04-15 | @ SEA | 9 | W 5-3 | 5-4 | 3 | 10,976 | Mike Witt | Mike Moore | Mike Witt | Bill Wilkinson | | 49 | 43 | 6 |
| 1988-04-16 | @ SEA | 10 | L 6-7 | 5-5 | 5 | 24,771 | Willie Fraser | Bill Swift | Ed Nunez | DeWayne Buice | | 55 | 50 | 5 |
| 1988-04-17 | @ SEA | 11 | W 7-4 | 6-5 | 3 | 14,641 | Kirk McCaskill | Steve Trout | Kirk McCaskill | Steve Trout | Ray Krawczyk | 62 | 54 | 8 |
| 1988-04-18 | @ OAK | 12 | L 4-5 | 6-6 | 4 | 20,644 | Dan Petry | Curt Young | Eric Plunk | DeWayne Buice | Dennis Eckersley | 66 | 59 | 7 |
| 1988-04-19 | @ OAK | 13 | L 3-8 | 6-7 | 5 | 8,183 | Chuck Finley | Dave Stewart | Dave Stewart | Chuck Finley | Dennis Eckersley | 69 | 67 | 2 |
| 1988-04-20 | @ OAK | 14 | L 8-9 | 6-8 | 5 | 14,299 | Mike Witt | Bob Welch | Gene Nelson | Donnie Moore | | 77 | 76 | 1 |
| 1988-04-21 | vs SEA | 15 | W 11-6 | 7-8 | 3 | 22,172 | Willie Fraser | Bill Swift | Willie Fraser | Ed Nunez | | 88 | 82 | 6 |
| 1988-04-22 | vs SEA | 16 | L 4-7 | 7-9 | 4 | 26,206 | Kirk McCaskill | Steve Trout | Steve Trout | Kirk McCaskill | Bill Wilkinson | 92 | 89 | 3 |
| 1988-04-23 | vs SEA | 17 | L 4-11 | 7-10 | 5 | 27,136 | Dan Petry | Mike Campbell | Mike Campbell | Dan Petry | | 96 | 100 | -4 |
| 1988-04-24 | vs SEA | 18 | L 2-4 | 7-11 | 6 | 42,725 | Chuck Finley | Mark Langston | Mark Langston | Chuck Finley | | 98 | 104 | -6 |
| 1988-04-26 | @ DET | 19 | L 0-6 | 7-12 | 6 | 11,973 | Mike Witt | Jeff Robinson | Jeff Robinson | Mike Witt | | 98 | 110 | -12 |
| 1988-04-27 | @ DET | 20 | W 4-3 | 8-12 | 6 | 10,927 | Willie Fraser | Doyle Alexander | Willie Fraser | Doyle Alexander | Donnie Moore | 102 | 113 | -11 |
| 1988-04-28 | @ DET | 21 | L 1-2 | 8-13 | 7 | 10,976 | Kirk McCaskill | Frank Tanana | Frank Tanana | Kirk McCaskill | Mike Henneman | 103 | 115 | -12 |
| 1988-04-29 | @ TOR | 22 | W 9-5 | 9-13 | 5 | 23,483 | Dan Petry | Jim Clancy | Bryan Harvey | David Wells | | 112 | 120 | -8 |
| 1988-04-30 | @ TOR | 23 | W 6-1 | 10-13 | 4 | 29,091 | Chuck Finley | John Cerutti | Chuck Finley | John Cerutti | | 118 | 121 | -3 |
| 1988-05-01 | @ TOR | 24 | L 4-6 | 10-14 | 4 | 36,115 | Mike Witt | Dave Stieb | Dave Stieb | Mike Witt | Tom Henke | 122 | 127 | -5 |
| 1988-05-02 | @ CLE | 25 | L 0-3 | 10-15 | 5 | 8,121 | Willie Fraser | Greg Swindell | Greg Swindell | Willie Fraser | | 122 | 130 | -8 |
| 1988-05-03 | @ CLE | 26 | W 8-4 | 11-15 | 4 | 6,912 | Kirk McCaskill | John Farrell | Donnie Moore | Dan Schatzeder | | 130 | 134 | -4 |
| 1988-05-04 | vs DET | 27 | L 0-1 | 11-16 | 5 | 26,020 | Dan Petry | Jack Morris | Jack Morris | Dan Petry | | 130 | 135 | -5 |
| 1988-05-05 | vs DET | 28 | L 5-8 | 11-17 | 5 | 23,821 | Chuck Finley | Walt Terrell | Guillermo Hernandez | Chuck Finley | Mike Henneman | 135 | 143 | -8 |
| 1988-05-06 | vs TOR | 29 | L 2-3 | 11-18 | 7 | 29,237 | Mike Witt | Dave Stieb | Dave Stieb | Mike Witt | Tom Henke | 137 | 146 | -9 |
| 1988-05-07 | vs TOR | 30 | L 4-9 | 11-19 | 7 | 32,630 | Willie Fraser | Mike Flanagan | Mike Flanagan | Willie Fraser | David Wells | 141 | 155 | -14 |
| 1988-05-08 | vs TOR | 31 | W 8-1 | 12-19 | 7 | 29,026 | Kirk McCaskill | Todd Stottlemyre | Kirk McCaskill | Todd Stottlemyre | | 149 | 156 | -7 |
| 1988-05-09 | vs CLE | 32 | W 2-1 | 13-19 | 6 | 22,123 | Dan Petry | John Farrell | Dan Petry | John Farrell | Bryan Harvey | 151 | 157 | -6 |
| 1988-05-10 | vs CLE | 33 | L 1-7 | 13-20 | 7 | 22,519 | Chuck Finley | Scott Bailes | Scott Bailes | Chuck Finley | | 152 | 164 | -12 |
| 1988-05-11 | vs CLE | 34 | L 3-4 | 13-21 | 7 | 23,713 | Mike Witt | Rich Yett | Doug Jones | Bryan Harvey | | 155 | 168 | -13 |
| 1988-05-13 | @ NYA | 35 | W 5-4 | 14-21 | 7 | 30,113 | Kirk McCaskill | Al Leiter | Willie Fraser | Cecilio Guante | DeWayne Buice | 160 | 172 | -12 |
| 1988-05-14 | @ NYA | 36 | L 2-6 | 14-22 | 7 | 33,119 | Dan Petry | Tommy John | Tommy John | Dan Petry | Dave Righetti | 162 | 178 | -16 |
| 1988-05-15 | @ NYA | 37 | L 2-9 | 14-23 | 7 | 51,006 | Chuck Finley | Charles Hudson | Charles Hudson | Chuck Finley | | 164 | 187 | -23 |
| 1988-05-18 | @ BAL | 38 | L 7-8 | 14-24 | 7 | 14,109 | Mike Witt | Jose Bautista | Jose Bautista | Mike Witt | Tom Niedenfuer | 171 | 195 | -24 |
| 1988-05-19 | @ BAL | 39 | W 2-1 | 16-24 | 7 | 0 | Kirk McCaskill | Mike Boddicker | Bryan Harvey | Dave J. Schmidt | | 173 | 196 | -23 |
| 1988-05-19 | @ BAL | 40 | W 9-6 | 16-24 | 7 | 18,409 | Dan Petry | Jay Tibbs | Stew Cliburn | Doug Sisk | Greg Minton | 182 | 202 | -20 |
| 1988-05-20 | @ BOS | 41 | W 4-2 | 17-24 | 7 | 31,032 | Chuck Finley | Roger Clemens | DeWayne Buice | Roger Clemens | Bryan Harvey | 186 | 204 | -18 |
| 1988-05-21 | @ BOS | 42 | L 4-8 | 17-25 | 7 | 32,180 | Ray Krawczyk | Bruce Hurst | Bruce Hurst | Ray Krawczyk | Lee Smith | 190 | 212 | -22 |
| 1988-05-22 | @ BOS | 43 | L 4-12 | 17-26 | 7 | 32,678 | Willie Fraser | Jeff Sellers | Bob Stanley | Willie Fraser | | 194 | 224 | -30 |
| 1988-05-23 | vs NYA | 44 | L 2-5 | 17-27 | 7 | 30,521 | Mike Witt | Richard Dotson | Cecilio Guante | Mike Witt | Dave Righetti | 196 | 229 | -33 |
| 1988-05-24 | vs NYA | 45 | L 3-5 | 17-28 | 7 | 32,805 | Kirk McCaskill | Al Leiter | Al Leiter | Kirk McCaskill | Dave Righetti | 199 | 234 | -35 |
| 1988-05-25 | vs NYA | 46 | L 2-4 | 17-29 | 7 | 48,198 | Dan Petry | Charles Hudson | Neil Allen | DeWayne Buice | | 201 | 238 | -37 |
| 1988-05-27 | vs BAL | 47 | W 4-2 | 18-29 | 7 | 24,458 | Chuck Finley | Jeff Ballard | Chuck Finley | Jeff Ballard | Bryan Harvey | 205 | 240 | -35 |
| 1988-05-28 | vs BAL | 48 | W 5-0 | 19-29 | 7 | 26,866 | Mike Witt | Jose Bautista | Mike Witt | Jose Bautista | | 210 | 240 | -30 |
| 1988-05-29 | vs BAL | 49 | L 2-3 | 19-30 | 7 | 24,860 | Kirk McCaskill | Mike Boddicker | Mike Boddicker | Greg Minton | Tom Niedenfuer | 212 | 243 | -31 |
| 1988-05-30 | vs BOS | 50 | L 2-5 | 19-31 | 7 | 46,598 | Dan Petry | Roger Clemens | Roger Clemens | Dan Petry | | 214 | 248 | -34 |
| 1988-05-31 | vs BOS | 51 | L 3-4 | 19-32 | 7 | 24,005 | Willie Fraser | Mike Smithson | Mike Smithson | Willie Fraser | | 217 | 252 | -35 |
| 1988-06-02 | @ MIL | 52 | L 4-9 | 19-33 | 7 | 14,414 | Chuck Finley | Odell Jones | Don August | Chuck Finley | Dan Plesac | 221 | 261 | -40 |
| 1988-06-03 | @ MIL | 53 | L 2-8 | 19-34 | 7 | 19,753 | Mike Witt | Tom Filer | Tom Filer | Mike Witt | | 223 | 269 | -46 |
| 1988-06-04 | @ MIL | 54 | L 0-1 | 19-35 | 7 | 43,287 | Dan Petry | Teddy Higuera | Teddy Higuera | Dan Petry | | 223 | 270 | -47 |
| 1988-06-05 | @ MIL | 55 | W 6-5 | 20-35 | 7 | 47,303 | Kirk McCaskill | Chris Bosio | DeWayne Buice | Chuck Crim | | 229 | 275 | -46 |
| 1988-06-06 | @ TEX | 56 | L 4-6 | 20-36 | 7 | 23,469 | Willie Fraser | Jose Guzman | Jose Guzman | Willie Fraser | | 233 | 281 | -48 |
| 1988-06-07 | @ TEX | 57 | W 1-0 | 21-36 | 7 | 22,549 | Chuck Finley | Charlie Hough | Chuck Finley | Charlie Hough | Bryan Harvey | 234 | 281 | -47 |
| 1988-06-08 | @ TEX | 58 | W 5-2 | 22-36 | 7 | 11,879 | Mike Witt | Ray Hayward | Mike Witt | Ray Hayward | Bryan Harvey | 239 | 283 | -44 |
| 1988-06-10 | vs KCA | 59 | W 1-0 | 23-36 | 7 | 38,642 | Dan Petry | Charlie Leibrandt | Dan Petry | Charlie Leibrandt | | 240 | 283 | -43 |
| 1988-06-11 | vs KCA | 60 | L 0-7 | 23-37 | 7 | 30,355 | Kirk McCaskill | Mark Gubicza | Mark Gubicza | Kirk McCaskill | | 240 | 290 | -50 |
| 1988-06-12 | vs KCA | 61 | L 4-6 | 23-38 | 7 | 36,931 | Willie Fraser | Ted Power | Ted Power | Willie Fraser | | 244 | 296 | -52 |
| 1988-06-13 | vs KCA | 62 | L 3-5 | 23-39 | 7 | 23,111 | Chuck Finley | Floyd Bannister | Floyd Bannister | Chuck Finley | Steve Farr | 247 | 301 | -54 |
| 1988-06-14 | vs TEX | 63 | W 3-0 | 24-39 | 7 | 23,312 | Mike Witt | Ray Hayward | Mike Witt | Ray Hayward | | 250 | 301 | -51 |
| 1988-06-15 | vs TEX | 64 | L 3-6 | 24-40 | 7 | 23,241 | Dan Petry | Jeff Russell | Jeff Russell | DeWayne Buice | | 253 | 307 | -54 |
| 1988-06-16 | vs TEX | 65 | W 3-0 | 25-40 | 7 | 21,754 | Kirk McCaskill | Paul Kilgus | Kirk McCaskill | Paul Kilgus | | 256 | 307 | -51 |
| 1988-06-17 | @ KCA | 66 | W 9-7 | 26-40 | 6 | 33,236 | Willie Fraser | Ted Power | Stew Cliburn | Gene Garber | | 265 | 314 | -49 |
| 1988-06-18 | @ KCA | 67 | W 6-3 | 27-40 | 6 | 40,642 | Chuck Finley | Floyd Bannister | Greg Minton | Jerry Gleaton | | 271 | 317 | -46 |
| 1988-06-19 | @ KCA | 68 | W 5-0 | 28-40 | 6 | 36,674 | Mike Witt | Bret Saberhagen | Mike Witt | Bret Saberhagen | | 276 | 317 | -41 |
| 1988-06-20 | @ MIN | 69 | W 6-5 | 29-40 | 6 | 26,501 | Dan Petry | Allan Anderson | Donnie Moore | Allan Anderson | | 282 | 322 | -40 |
| 1988-06-21 | @ MIN | 70 | W 5-4 | 30-40 | 6 | 29,550 | Kirk McCaskill | Freddie Toliver | Greg Minton | Mark Portugal | Bryan Harvey | 287 | 326 | -39 |
| 1988-06-22 | @ MIN | 71 | L 1-3 | 30-41 | 6 | 41,755 | Willie Fraser | Frank Viola | Frank Viola | Willie Fraser | | 288 | 329 | -41 |
| 1988-06-24 | vs MIL | 72 | L 4-5 | 30-42 | 6 | 40,241 | Chuck Finley | Bill Wegman | Paul Mirabella | Bryan Harvey | Chuck Crim | 292 | 334 | -42 |
| 1988-06-25 | vs MIL | 73 | W 7-3 | 31-42 | 6 | 31,626 | Mike Witt | Tom Filer | Mike Witt | Tom Filer | | 299 | 337 | -38 |
| 1988-06-26 | vs MIL | 74 | W 4-2 | 32-42 | 6 | 34,569 | Willie Fraser | Teddy Higuera | Willie Fraser | Teddy Higuera | Bryan Harvey | 303 | 339 | -36 |
| 1988-06-27 | vs MIN | 75 | W 16-7 | 33-42 | 6 | 22,167 | Kirk McCaskill | Freddie Toliver | Kirk McCaskill | Freddie Toliver | | 319 | 346 | -27 |
| 1988-06-28 | vs MIN | 76 | L 2-8 | 33-43 | 6 | 27,618 | Jack Lazorko | Bert Blyleven | Bert Blyleven | Jack Lazorko | | 321 | 354 | -33 |
| 1988-06-29 | vs MIN | 77 | W 2-1 | 34-43 | 6 | 29,050 | Chuck Finley | Allan Anderson | Chuck Finley | Allan Anderson | Bryan Harvey | 323 | 355 | -32 |
| 1988-07-01 | @ DET | 78 | L 0-11 | 34-44 | 6 | 23,762 | Mike Witt | Doyle Alexander | Doyle Alexander | Mike Witt | | 323 | 366 | -43 |
| 1988-07-02 | @ DET | 79 | L 1-6 | 34-45 | 6 | 30,548 | Willie Fraser | Jeff Robinson | Jeff Robinson | Willie Fraser | | 324 | 372 | -48 |
| 1988-07-03 | @ DET | 80 | W 10-4 | 35-45 | 6 | 32,176 | Kirk McCaskill | Jack Morris | Kirk McCaskill | Jack Morris | | 334 | 376 | -42 |
| 1988-07-04 | @ TOR | 81 | W 11-6 | 36-45 | 6 | 30,584 | Jack Lazorko | Jim Clancy | Stew Cliburn | Jim Clancy | | 345 | 382 | -37 |
| 1988-07-05 | @ TOR | 82 | L 1-4 | 36-46 | 6 | 32,284 | Mike Witt | Jimmy Key | Jimmy Key | Mike Witt | Duane Ward | 346 | 386 | -40 |
| 1988-07-06 | @ TOR | 83 | W 5-4 | 37-46 | 6 | 31,312 | Willie Fraser | Dave Stieb | Bryan Harvey | David Wells | Donnie Moore | 351 | 390 | -39 |
| 1988-07-07 | @ CLE | 84 | W 7-1 | 38-46 | 6 | 10,889 | Terry Clark | John Farrell | Terry Clark | John Farrell | Greg Minton | 358 | 391 | -33 |
| 1988-07-08 | @ CLE | 85 | W 10-6 | 39-46 | 6 | 19,588 | Kirk McCaskill | Buddy Black | Kirk McCaskill | Buddy Black | Bryan Harvey | 368 | 397 | -29 |
| 1988-07-09 | @ CLE | 86 | W 8-5 | 40-46 | 6 | 15,487 | Mike Witt | Tom Candiotti | Bryan Harvey | Doug Jones | Donnie Moore | 376 | 402 | -26 |
| 1988-07-10 | @ CLE | 87 | W 7-5 | 41-46 | 5 | 20,050 | Willie Fraser | Scott Bailes | Willie Fraser | Scott Bailes | Greg Minton | 383 | 407 | -24 |
| 1988-07-14 | vs DET | 88 | W 2-0 | 42-46 | 4 | 30,165 | Kirk McCaskill | Jack Morris | Kirk McCaskill | Jack Morris | | 385 | 407 | -22 |
| 1988-07-15 | vs DET | 89 | W 6-4 | 43-46 | 4 | 34,829 | Mike Witt | Doyle Alexander | Mike Witt | Doyle Alexander | Bryan Harvey | 391 | 411 | -20 |
| 1988-07-16 | vs DET | 90 | L 1-10 | 43-47 | 4 | 30,082 | Willie Fraser | Jeff Robinson | Jeff Robinson | Willie Fraser | | 392 | 421 | -29 |
| 1988-07-17 | vs DET | 91 | W 4-0 | 44-47 | 4 | 36,030 | Terry Clark | Frank Tanana | Terry Clark | Frank Tanana | | 396 | 421 | -25 |
| 1988-07-18 | vs TOR | 92 | L 2-12 | 44-48 | 4 | 24,241 | Chuck Finley | Jeff Musselman | Jeff Musselman | Chuck Finley | Jim Clancy | 398 | 433 | -35 |
| 1988-07-19 | vs TOR | 93 | L 6-7 | 44-49 | 4 | 24,131 | Kirk McCaskill | Mike Flanagan | Tom Henke | Bryan Harvey | | 404 | 440 | -36 |
| 1988-07-20 | vs TOR | 94 | W 7-6 | 45-49 | 4 | 25,598 | Willie Fraser | Jimmy Key | Greg Minton | John Cerutti | Donnie Moore | 411 | 446 | -35 |
| 1988-07-22 | vs CLE | 95 | W 7-4 | 46-49 | 4 | 27,403 | Terry Clark | Tom Candiotti | Terry Clark | Tom Candiotti | | 418 | 450 | -32 |
| 1988-07-23 | vs CLE | 96 | W 5-4 | 47-49 | 4 | 34,977 | Chuck Finley | Scott Bailes | Stew Cliburn | Don Gordon | Greg Minton | 423 | 454 | -31 |
| 1988-07-24 | vs CLE | 97 | L 2-9 | 47-50 | 4 | 31,015 | Willie Fraser | Greg Swindell | Greg Swindell | Willie Fraser | | 425 | 463 | -38 |
| 1988-07-25 | vs OAK | 98 | W 2-1 | 48-50 | 4 | 30,928 | Kirk McCaskill | Dave Stewart | Kirk McCaskill | Dave Stewart | | 427 | 464 | -37 |
| 1988-07-26 | vs OAK | 99 | L 2-6 | 48-51 | 4 | 35,838 | Mike Witt | Storm Davis | Storm Davis | Mike Witt | | 429 | 470 | -41 |
| 1988-07-27 | vs OAK | 100 | W 9-8 | 49-51 | 4 | 33,714 | Terry Clark | Todd Burns | Donnie Moore | Jim Corsi | | 438 | 478 | -40 |
| 1988-07-28 | @ CHA | 101 | W 7-6 | 50-51 | 3 | 14,527 | Chuck Finley | Dave LaPoint | Donnie Moore | Ricky Horton | | 445 | 484 | -39 |
| 1988-07-29 | @ CHA | 102 | W 4-2 | 51-51 | 3 | 16,802 | Willie Fraser | Bill Long | Willie Fraser | Bill Long | Bryan Harvey | 449 | 486 | -37 |
| 1988-07-30 | @ CHA | 103 | W 15-14 | 52-51 | 3 | 17,422 | Kirk McCaskill | Jerry Reuss | Sherman Corbett | John Davis | | 464 | 500 | -36 |
| 1988-07-31 | @ CHA | 104 | W 7-5 | 53-51 | 3 | 13,370 | Mike Witt | Jack McDowell | Mike Witt | Ricky Horton | Greg Minton | 471 | 505 | -34 |
| 1988-08-01 | @ SEA | 105 | W 8-4 | 54-51 | 3 | 11,584 | Terry Clark | Bill Swift | Terry Clark | Bill Swift | | 479 | 509 | -30 |
| 1988-08-02 | @ SEA | 106 | W 10-2 | 55-51 | 3 | 8,565 | Chuck Finley | Steve Trout | Chuck Finley | Steve Trout | | 489 | 511 | -22 |
| 1988-08-03 | @ SEA | 107 | L 7-8 | 55-52 | 3 | 9,574 | Kirk McCaskill | Mark Langston | Mike Schooler | Bryan Harvey | | 496 | 519 | -23 |
| 1988-08-05 | vs CHA | 108 | W 6-5 | 56-53 | 3 | 0 | Mike Witt | Jack McDowell | Sherman Corbett | Donn Pall | | 502 | 524 | -22 |
| 1988-08-05 | vs CHA | 109 | L 4-5 | 56-53 | 3 | 43,461 | Willie Fraser | Jerry Reuss | Ricky Horton | Greg Minton | Bobby Thigpen | 506 | 529 | -23 |
| 1988-08-06 | vs CHA | 110 | W 7-5 | 57-53 | 3 | 47,967 | Terry Clark | Melido Perez | Terry Clark | Melido Perez | Greg Minton | 513 | 534 | -21 |
| 1988-08-07 | vs CHA | 111 | L 3-6 | 57-54 | 3 | 29,240 | Chuck Finley | Dave LaPoint | Dave LaPoint | Chuck Finley | Bobby Thigpen | 516 | 540 | -24 |
| 1988-08-08 | vs SEA | 112 | L 3-4 | 57-55 | 3 | 23,506 | Kirk McCaskill | Mark Langston | Mark Langston | Kirk McCaskill | Mike Schooler | 519 | 544 | -25 |
| 1988-08-09 | vs SEA | 113 | L 1-4 | 57-56 | 4 | 24,617 | Mike Witt | Mike Moore | Mike Moore | Mike Witt | Michael Jackson | 520 | 548 | -28 |
| 1988-08-10 | vs SEA | 114 | W 2-1 | 58-56 | 4 | 24,653 | Willie Fraser | Scott Bankhead | Willie Fraser | Scott Bankhead | | 522 | 549 | -27 |
| 1988-08-11 | @ OAK | 115 | L 2-7 | 58-57 | 4 | 20,195 | Terry Clark | Storm Davis | Dennis Eckersley | Terry Clark | | 524 | 556 | -32 |
| 1988-08-12 | @ OAK | 116 | L 0-4 | 58-58 | 4 | 34,518 | Chuck Finley | Todd Burns | Todd Burns | Chuck Finley | Greg Cadaret | 524 | 560 | -36 |
| 1988-08-13 | @ OAK | 117 | L 2-6 | 58-59 | 4 | 33,314 | Stew Cliburn | Bob Welch | Bob Welch | Stew Cliburn | Rick Honeycutt | 526 | 566 | -40 |
| 1988-08-14 | @ OAK | 118 | W 6-4 | 59-59 | 4 | 40,013 | Mike Witt | Dave Stewart | Mike Witt | Gene Nelson | Bryan Harvey | 532 | 570 | -38 |
| 1988-08-16 | @ NYA | 119 | W 15-6 | 60-59 | 4 | 30,214 | Willie Fraser | Rick Rhoden | Willie Fraser | Rick Rhoden | | 547 | 576 | -29 |
| 1988-08-17 | @ NYA | 120 | L 7-11 | 60-60 | 4 | 26,532 | Terry Clark | Dave Eiland | Scott Nielsen | Stew Cliburn | Dave Righetti | 554 | 587 | -33 |
| 1988-08-18 | @ NYA | 121 | W 7-1 | 61-60 | 4 | 26,044 | Chuck Finley | Tommy John | Chuck Finley | Tommy John | Greg Minton | 561 | 588 | -27 |
| 1988-08-19 | @ BAL | 122 | L 1-3 | 61-61 | 4 | 25,009 | Mike Witt | Dave J. Schmidt | Dave J. Schmidt | Mike Witt | Tom Niedenfuer | 562 | 591 | -29 |
| 1988-08-20 | @ BAL | 123 | L 2-3 | 61-62 | 4 | 17,092 | Jack Lazorko | Jose Bautista | Mark Williamson | Greg Minton | | 564 | 594 | -30 |
| 1988-08-21 | @ BAL | 124 | W 3-2 | 62-62 | 4 | 26,052 | Willie Fraser | Jay Tibbs | Willie Fraser | Jay Tibbs | Sherman Corbett | 567 | 596 | -29 |
| 1988-08-22 | @ BOS | 125 | L 2-6 | 62-63 | 4 | 33,828 | Terry Clark | Bruce Hurst | Bruce Hurst | Terry Clark | | 569 | 602 | -33 |
| 1988-08-23 | @ BOS | 126 | L 2-10 | 62-64 | 4 | 34,313 | Chuck Finley | Mike Boddicker | Mike Boddicker | Chuck Finley | | 571 | 612 | -41 |
| 1988-08-24 | @ BOS | 127 | W 4-3 | 63-64 | 4 | 32,522 | Mike Witt | Roger Clemens | Mike Witt | Roger Clemens | Bryan Harvey | 575 | 615 | -40 |
| 1988-08-26 | vs NYA | 128 | W 7-6 | 64-64 | 4 | 44,293 | Willie Fraser | Rick Rhoden | Bryan Harvey | Steve Shields | | 582 | 621 | -39 |
| 1988-08-27 | vs NYA | 129 | W 12-0 | 65-64 | 4 | 34,908 | Terry Clark | Charles Hudson | Terry Clark | Charles Hudson | | 594 | 621 | -27 |
| 1988-08-28 | vs NYA | 130 | W 13-2 | 66-64 | 4 | 40,406 | Chuck Finley | Tommy John | Chuck Finley | Tommy John | | 607 | 623 | -16 |
| 1988-08-29 | vs BAL | 131 | W 4-2 | 67-64 | 4 | 21,974 | Mike Witt | Jeff Ballard | Mike Witt | Jeff Ballard | | 611 | 625 | -14 |
| 1988-08-30 | vs BAL | 132 | L 2-5 | 67-65 | 4 | 22,867 | Dan Petry | Dave J. Schmidt | Dave J. Schmidt | Dan Petry | Tom Niedenfuer | 613 | 630 | -17 |
| 1988-08-31 | vs BAL | 133 | W 7-5 | 68-65 | 4 | 21,921 | Willie Fraser | Jay Tibbs | Bryan Harvey | Mark Williamson | | 620 | 635 | -15 |
| 1988-09-01 | vs BOS | 134 | L 2-4 | 68-66 | 4 | 27,771 | Terry Clark | Wes Gardner | Wes Gardner | Terry Clark | Lee Smith | 622 | 639 | -17 |
| 1988-09-02 | vs BOS | 135 | W 3-2 | 69-66 | 4 | 29,325 | Chuck Finley | Bruce Hurst | Chuck Finley | Bruce Hurst | Bryan Harvey | 625 | 641 | -16 |
| 1988-09-03 | vs BOS | 136 | W 2-1 | 70-66 | 4 | 33,376 | Mike Witt | Mike Boddicker | Mike Witt | Dennis Lamp | | 627 | 642 | -15 |
| 1988-09-04 | vs BOS | 137 | L 5-6 | 70-67 | 4 | 30,224 | Dan Petry | Roger Clemens | Bob Stanley | Bryan Harvey | Lee Smith | 632 | 648 | -16 |
| 1988-09-05 | @ KCA | 138 | W 4-2 | 71-67 | 4 | 25,855 | Willie Fraser | Charlie Leibrandt | Willie Fraser | Charlie Leibrandt | Bryan Harvey | 636 | 650 | -14 |
| 1988-09-06 | @ KCA | 139 | L 2-3 | 71-68 | 4 | 16,645 | Terry Clark | Mark Gubicza | Steve Farr | Greg Minton | | 638 | 653 | -15 |
| 1988-09-07 | @ KCA | 140 | L 2-4 | 71-69 | 4 | 16,600 | Chuck Finley | Floyd Bannister | Floyd Bannister | Chuck Finley | Steve Farr | 640 | 657 | -17 |
| 1988-09-08 | @ TEX | 141 | W 4-3 | 72-69 | 4 | 7,455 | Mike Witt | Jeff Russell | Mike Witt | Mitch Williams | Bryan Harvey | 644 | 660 | -16 |
| 1988-09-09 | @ TEX | 142 | W 5-3 | 73-69 | 4 | 14,883 | Dan Petry | Bobby Witt | Greg Minton | Bobby Witt | Bryan Harvey | 649 | 663 | -14 |
| 1988-09-10 | @ TEX | 143 | L 2-3 | 73-70 | 4 | 22,972 | Willie Fraser | Paul Kilgus | Ed Vande Berg | Mike Cook | | 651 | 666 | -15 |
| 1988-09-11 | @ TEX | 144 | L 3-8 | 73-71 | 4 | 9,679 | Terry Clark | Charlie Hough | Charlie Hough | Terry Clark | Ed Vande Berg | 654 | 674 | -20 |
| 1988-09-13 | vs KCA | 145 | L 3-4 | 73-72 | 4 | 22,522 | Chuck Finley | Bret Saberhagen | Bret Saberhagen | Chuck Finley | Steve Farr | 657 | 678 | -21 |
| 1988-09-14 | vs KCA | 146 | L 2-4 | 73-73 | 4 | 21,550 | Mike Witt | Floyd Bannister | Floyd Bannister | Mike Witt | Steve Farr | 659 | 682 | -23 |
| 1988-09-15 | vs KCA | 147 | L 1-2 | 73-74 | 4 | 22,638 | Dan Petry | Charlie Leibrandt | Charlie Leibrandt | Dan Petry | | 660 | 684 | -24 |
| 1988-09-16 | vs TEX | 148 | W 7-2 | 74-74 | 4 | 25,453 | Willie Fraser | Paul Kilgus | Willie Fraser | Paul Kilgus | | 667 | 686 | -19 |
| 1988-09-17 | vs TEX | 149 | L 4-7 | 74-75 | 4 | 23,197 | Terry Clark | Charlie Hough | Charlie Hough | Terry Clark | Dwayne Henry | 671 | 693 | -22 |
| 1988-09-18 | vs TEX | 150 | W 6-5 | 75-75 | 4 | 23,936 | Chuck Finley | Jeff Russell | Bryan Harvey | Mitch Williams | | 677 | 698 | -21 |
| 1988-09-19 | vs MIL | 151 | L 2-4 | 75-76 | 4 | 20,207 | Mike Witt | Bill Wegman | Bill Wegman | Mike Witt | Chuck Crim | 679 | 702 | -23 |
| 1988-09-20 | vs MIL | 152 | L 5-6 | 75-77 | 4 | 20,220 | Dan Petry | Teddy Higuera | Teddy Higuera | Greg Minton | Chris Bosio | 684 | 708 | -24 |
| 1988-09-21 | vs MIL | 153 | L 3-10 | 75-78 | 4 | 22,080 | Willie Fraser | Don August | Don August | Willie Fraser | Paul Mirabella | 687 | 718 | -31 |
| 1988-09-22 | vs MIN | 154 | L 2-6 | 75-79 | 4 | 20,338 | Terry Clark | Allan Anderson | Allan Anderson | Terry Clark | | 689 | 724 | -35 |
| 1988-09-23 | vs MIN | 155 | L 1-7 | 75-80 | 4 | 23,902 | Chuck Finley | Charlie Lea | Roy Smith | Chuck Finley | | 690 | 731 | -41 |
| 1988-09-24 | vs MIN | 156 | L 2-3 | 75-81 | 4 | 25,290 | Mike Witt | Freddie Toliver | Jeff Reardon | Mike Witt | | 692 | 734 | -42 |
| 1988-09-25 | vs MIN | 157 | L 2-6 | 75-82 | 4 | 34,745 | Dan Petry | Frank Viola | Frank Viola | Dan Petry | Juan Berenguer | 694 | 740 | -46 |
| 1988-09-27 | @ MIL | 158 | L 5-6 | 75-83 | 4 | 10,728 | Willie Fraser | Don August | Don August | Willie Fraser | Chris Bosio | 699 | 746 | -47 |
| 1988-09-28 | @ MIL | 159 | L 3-4 | 75-84 | 4 | 12,123 | Chuck Finley | Juan Nieves | Chuck Crim | Sherman Corbett | Paul Mirabella | 702 | 750 | -48 |
| 1988-09-30 | @ MIN | 160 | L 5-8 | 75-85 | 4 | 34,898 | Mike Witt | Frank Viola | Frank Viola | Mike Witt | Jeff Reardon | 707 | 758 | -51 |
| 1988-10-01 | @ MIN | 161 | L 5-10 | 75-86 | 4 | 52,625 | Dan Petry | Charlie Lea | Charlie Lea | Dan Petry | Les Straker | 712 | 768 | -56 |
| 1988-10-02 | @ MIN | 162 | L 2-3 | 75-87 | 4 | 35,952 | Willie Fraser | Roy Smith | Roy Smith | Willie Fraser | Jeff Reardon | 714 | 771 | -57 |