| 1998-03-31 | @ TEX | 1 | W 9-2 | 1-0 | 1 | 45,909 | Jaime Navarro | John Burkett | Jaime Navarro | John Burkett | | 9 | 2 | 7 |
| 1998-04-02 | @ TEX | 2 | L 4-20 | 1-1 | 2 | 32,663 | Mike Sirotka | Aaron Sele | Aaron Sele | Mike Sirotka | Roger Pavlik | 13 | 22 | -9 |
| 1998-04-03 | @ TBA | 3 | W 10-4 | 2-1 | 2 | 31,816 | James Baldwin | Rick Gorecki | James Baldwin | Rick Gorecki | | 23 | 26 | -3 |
| 1998-04-04 | @ TBA | 4 | L 2-8 | 2-2 | 3 | 36,599 | Scott Eyre | Dennis Springer | Dennis Springer | Scott Eyre | | 25 | 34 | -9 |
| 1998-04-05 | @ TBA | 5 | L 0-5 | 2-3 | 3 | 33,733 | Jason Bere | Wilson Alvarez | Wilson Alvarez | Jason Bere | | 25 | 39 | -14 |
| 1998-04-06 | vs TEX | 6 | W 5-4 | 3-3 | 2 | 25,358 | Jaime Navarro | Bobby Witt | Keith Foulke | Roger Pavlik | Matt Karchner | 30 | 43 | -13 |
| 1998-04-09 | vs TEX | 7 | L 0-11 | 3-4 | 3 | 10,654 | James Baldwin | Aaron Sele | Aaron Sele | James Baldwin | | 30 | 54 | -24 |
| 1998-04-10 | vs TBA | 8 | W 3-0 | 4-4 | 2 | 13,563 | Mike Sirotka | Tony Saunders | Mike Sirotka | Tony Saunders | Matt Karchner | 33 | 54 | -21 |
| 1998-04-11 | vs TBA | 9 | L 1-5 | 4-5 | 3 | 17,332 | Jason Bere | Rick Gorecki | Rick Gorecki | Jason Bere | | 34 | 59 | -25 |
| 1998-04-12 | vs TBA | 10 | L 1-4 | 4-6 | 3 | 14,004 | Jaime Navarro | Wilson Alvarez | Wilson Alvarez | Jaime Navarro | Roberto Hernandez | 35 | 63 | -28 |
| 1998-04-14 | @ BAL | 11 | L 3-4 | 4-7 | 4 | 43,039 | Scott Eyre | Jimmy Key | Jimmy Key | Scott Eyre | Jesse Orosco | 38 | 67 | -29 |
| 1998-04-15 | @ BAL | 12 | W 7-6 | 5-7 | 4 | 46,546 | James Baldwin | Doug Drabek | James Baldwin | Doug Drabek | Matt Karchner | 45 | 73 | -28 |
| 1998-04-16 | @ BAL | 13 | W 8-2 | 6-7 | 3 | 48,093 | Mike Sirotka | Mike Mussina | Mike Sirotka | Mike Mussina | | 53 | 75 | -22 |
| 1998-04-17 | @ TOR | 14 | L 1-6 | 6-8 | 4 | 28,240 | Jason Bere | Roger Clemens | Roger Clemens | Jason Bere | | 54 | 81 | -27 |
| 1998-04-18 | @ TOR | 15 | L 4-9 | 6-9 | 4 | 29,065 | Jaime Navarro | Pat Hentgen | Pat Hentgen | Jaime Navarro | | 58 | 90 | -32 |
| 1998-04-19 | @ TOR | 16 | L 4-5 | 6-10 | 4 | 31,265 | Scott Eyre | Juan Guzman | Chris Carpenter | Carlos Castillo | | 62 | 95 | -33 |
| 1998-04-21 | @ CLE | 17 | L 6-14 | 6-11 | 4 | 42,836 | James Baldwin | Chad Ogea | Jose Mesa | James Baldwin | | 68 | 109 | -41 |
| 1998-04-22 | @ CLE | 18 | W 14-7 | 7-11 | 4 | 42,840 | Mike Sirotka | Charles Nagy | Mike Sirotka | Charles Nagy | | 82 | 116 | -34 |
| 1998-04-23 | @ CLE | 19 | L 4-5 | 7-12 | 4 | 42,865 | Jason Bere | Jaret Wright | Eric Plunk | Tony Castillo | Michael Jackson | 86 | 121 | -35 |
| 1998-04-24 | vs TOR | 20 | L 1-3 | 7-13 | 4 | 14,198 | Jaime Navarro | Pat Hentgen | Pat Hentgen | Jaime Navarro | Randy Myers | 87 | 124 | -37 |
| 1998-04-25 | vs TOR | 21 | W 8-1 | 8-13 | 4 | 14,457 | Scott Eyre | Juan Guzman | Scott Eyre | Juan Guzman | | 95 | 125 | -30 |
| 1998-04-26 | vs TOR | 22 | W 5-5 | 9-13 | 4 | 13,705 | James Baldwin | Erik Hanson | | | | 100 | 130 | -30 |
| 1998-04-27 | vs CLE | 23 | W 10-3 | 10-13 | 2 | 13,575 | Mike Sirotka | Chad Ogea | Mike Sirotka | Chad Ogea | | 110 | 133 | -23 |
| 1998-04-28 | vs CLE | 24 | L 1-4 | 10-14 | 2 | 13,208 | Jason Bere | Charles Nagy | Charles Nagy | Matt Karchner | Michael Jackson | 111 | 137 | -26 |
| 1998-04-29 | vs BAL | 25 | W 16-7 | 11-14 | 2 | 12,262 | Jaime Navarro | Sidney Ponson | Jaime Navarro | Sidney Ponson | | 127 | 144 | -17 |
| 1998-04-30 | vs BAL | 26 | L 1-4 | 11-15 | 3 | 11,772 | Scott Eyre | Jimmy Key | Jimmy Key | Scott Eyre | Armando Benitez | 128 | 148 | -20 |
| 1998-05-01 | @ ANA | 27 | L 1-7 | 11-16 | 3 | 36,485 | James Baldwin | Omar Olivares | Shigetoshi Hasegawa | James Baldwin | | 129 | 155 | -26 |
| 1998-05-02 | @ ANA | 28 | L 3-5 | 11-17 | 4 | 37,500 | Mike Sirotka | Chuck Finley | Rich DeLucia | Mike Sirotka | Troy Percival | 132 | 160 | -28 |
| 1998-05-03 | @ ANA | 29 | W 12-1 | 12-17 | 2 | 34,920 | Jason Bere | Jason Dickson | Jason Bere | Jason Dickson | | 144 | 161 | -17 |
| 1998-05-04 | @ ANA | 30 | W 6-5 | 13-17 | 2 | 15,997 | Jaime Navarro | Allen Watson | Tony Castillo | Rich DeLucia | Matt Karchner | 150 | 166 | -16 |
| 1998-05-05 | @ SEA | 31 | L 1-8 | 13-18 | 2 | 22,760 | Scott Eyre | Jeff Fassero | Jeff Fassero | Scott Eyre | | 151 | 174 | -23 |
| 1998-05-06 | @ SEA | 32 | L 9-10 | 13-19 | 2 | 21,243 | James Baldwin | Ken Cloude | Heathcliff Slocumb | Carlos Castillo | Bobby Ayala | 160 | 184 | -24 |
| 1998-05-08 | @ OAK | 33 | W 5-3 | 14-19 | 2 | 9,509 | Mike Sirotka | Mike Oquist | Mike Sirotka | Mike Fetters | | 165 | 187 | -22 |
| 1998-05-09 | @ OAK | 34 | L 7-15 | 14-20 | 2 | 13,167 | Jason Bere | Kenny Rogers | Kenny Rogers | Jason Bere | Mike Fetters | 172 | 202 | -30 |
| 1998-05-10 | @ OAK | 35 | W 4-3 | 15-20 | 2 | 13,309 | Jaime Navarro | Blake Stein | Jaime Navarro | Blake Stein | Bill Simas | 176 | 205 | -29 |
| 1998-05-12 | vs ANA | 36 | W 5-2 | 16-20 | 2 | 13,050 | Scott Eyre | Omar Olivares | Carlos Castillo | Omar Olivares | | 181 | 207 | -26 |
| 1998-05-13 | vs ANA | 37 | L 3-8 | 16-21 | 2 | 13,498 | Mike Sirotka | Allen Watson | Allen Watson | Mike Sirotka | | 184 | 215 | -31 |
| 1998-05-14 | vs SEA | 38 | W 5-3 | 17-21 | 2 | 15,007 | Jason Bere | Randy Johnson | Tom Fordham | Randy Johnson | Bill Simas | 189 | 218 | -29 |
| 1998-05-15 | vs SEA | 39 | W 6-3 | 18-21 | 2 | 16,127 | Jaime Navarro | Bill Swift | Jaime Navarro | Bill Swift | Keith Foulke | 195 | 221 | -26 |
| 1998-05-16 | vs OAK | 40 | L 3-11 | 18-22 | 2 | 24,024 | Carlos Castillo | Blake Stein | Blake Stein | Carlos Castillo | | 198 | 232 | -34 |
| 1998-05-17 | vs OAK | 41 | L 7-9 | 18-23 | 2 | 19,002 | Scott Eyre | Tom Candiotti | Buddy Groom | Bill Simas | Billy Taylor | 205 | 241 | -36 |
| 1998-05-18 | vs OAK | 42 | L 0-14 | 18-24 | 2 | 14,387 | Mike Sirotka | Jimmy Haynes | Jimmy Haynes | Mike Sirotka | | 205 | 255 | -50 |
| 1998-05-19 | @ BOS | 43 | W 9-5 | 19-24 | 2 | 27,121 | Jason Bere | Bret Saberhagen | Jason Bere | Bret Saberhagen | | 214 | 260 | -46 |
| 1998-05-20 | @ BOS | 44 | L 2-6 | 19-25 | 2 | 26,953 | Jaime Navarro | Pedro Martinez | Pedro Martinez | Jaime Navarro | Tom Gordon | 216 | 266 | -50 |
| 1998-05-22 | vs DET | 45 | L 5-9 | 19-26 | 2 | 13,324 | Scott Eyre | Justin Thompson | Justin Thompson | Scott Eyre | | 221 | 275 | -54 |
| 1998-05-23 | vs DET | 46 | W 7-1 | 20-26 | 2 | 18,986 | Mike Sirotka | Brian Moehler | Mike Sirotka | Brian Moehler | | 228 | 276 | -48 |
| 1998-05-24 | vs DET | 47 | L 4-8 | 20-27 | 3 | 17,554 | Jason Bere | A.J. Sager | A.J. Sager | Jason Bere | | 232 | 284 | -52 |
| 1998-05-25 | vs NYA | 48 | L 0-12 | 20-28 | 3 | 19,812 | Jaime Navarro | Hideki Irabu | Hideki Irabu | Jaime Navarro | | 232 | 296 | -64 |
| 1998-05-26 | vs NYA | 49 | L 5-7 | 20-29 | 3 | 14,596 | Jim Parque | Andy Pettitte | Jeff Nelson | Keith Foulke | Mariano Rivera | 237 | 303 | -66 |
| 1998-05-27 | vs NYA | 50 | W 12-9 | 21-29 | 3 | 15,232 | Scott Eyre | Ramiro Mendoza | Bill Simas | Jeff Nelson | Matt Karchner | 249 | 312 | -63 |
| 1998-05-28 | @ DET | 51 | W 11-7 | 22-29 | 3 | 10,634 | Mike Sirotka | Justin Thompson | Matt Karchner | Roberto Duran | | 260 | 319 | -59 |
| 1998-05-29 | @ DET | 52 | L 7-8 | 22-30 | 3 | 20,078 | Jason Bere | A.J. Sager | Dean Crow | Carlos Castillo | Todd Jones | 267 | 327 | -60 |
| 1998-05-30 | @ DET | 53 | L 0-6 | 22-31 | 4 | 17,946 | Jaime Navarro | Brian Moehler | Brian Moehler | Jaime Navarro | | 267 | 333 | -66 |
| 1998-05-31 | @ DET | 54 | W 8-2 | 23-31 | 3 | 27,200 | Jim Parque | Frank Castillo | Jim Parque | Frank Castillo | | 275 | 335 | -60 |
| 1998-06-01 | @ NYA | 55 | L 4-5 | 23-32 | 3 | 19,131 | Scott Eyre | Ramiro Mendoza | Jeff Nelson | Matt Karchner | | 279 | 340 | -61 |
| 1998-06-02 | @ NYA | 56 | L 3-6 | 23-33 | 3 | 22,599 | Mike Sirotka | David Wells | David Wells | Mike Sirotka | Mariano Rivera | 282 | 346 | -64 |
| 1998-06-03 | @ KCA | 57 | W 10-5 | 24-33 | 3 | 13,280 | Jason Bere | Pat Rapp | Carlos Castillo | Pat Rapp | | 292 | 351 | -59 |
| 1998-06-04 | @ KCA | 58 | W 7-1 | 25-33 | 3 | 16,590 | Jaime Navarro | Glendon Rusch | Jaime Navarro | Glendon Rusch | | 299 | 352 | -53 |
| 1998-06-05 | @ CHN | 59 | L 5-6 | 25-34 | 3 | 38,097 | Jim Parque | Steve Trachsel | Terry Mulholland | Tony Castillo | | 304 | 358 | -54 |
| 1998-06-06 | @ CHN | 60 | L 6-7 | 25-35 | 3 | 38,232 | Scott Eyre | Kevin Tapani | Kevin Tapani | Scott Eyre | Rod Beck | 310 | 365 | -55 |
| 1998-06-07 | @ CHN | 61 | L 7-13 | 25-36 | 3 | 39,320 | Mike Sirotka | Geremi Gonzalez | Geremi Gonzalez | Mike Sirotka | | 317 | 378 | -61 |
| 1998-06-08 | vs SLN | 62 | W 8-6 | 26-36 | 3 | 23,087 | Jason Bere | Mark Petkovsek | Jason Bere | Mark Petkovsek | Matt Karchner | 325 | 384 | -59 |
| 1998-06-09 | vs SLN | 63 | L 4-5 | 26-37 | 3 | 15,295 | Jaime Navarro | Juan Acevedo | Lance Painter | Jaime Navarro | Jeff Brantley | 329 | 389 | -60 |
| 1998-06-10 | vs SLN | 64 | W 10-8 | 27-37 | 3 | 16,151 | Jim Parque | Kent Bottenfield | Matt Karchner | Sean Lowe | | 339 | 397 | -58 |
| 1998-06-12 | @ MIN | 65 | L 7-8 | 27-38 | 3 | 10,520 | Scott Eyre | Eric Milton | Rick Aguilera | Bill Simas | | 346 | 405 | -59 |
| 1998-06-13 | @ MIN | 66 | W 3-2 | 28-38 | 3 | 16,593 | Mike Sirotka | Bob Tewksbury | Mike Sirotka | Bob Tewksbury | Matt Karchner | 349 | 407 | -58 |
| 1998-06-14 | @ MIN | 67 | L 1-2 | 28-39 | 3 | 14,945 | Jaime Navarro | LaTroy Hawkins | LaTroy Hawkins | Jaime Navarro | Rick Aguilera | 350 | 409 | -59 |
| 1998-06-15 | vs BOS | 68 | W 3-2 | 29-39 | 3 | 16,130 | Jim Parque | Bret Saberhagen | Jim Parque | Bret Saberhagen | Matt Karchner | 353 | 411 | -58 |
| 1998-06-16 | vs BOS | 69 | L 1-6 | 29-40 | 3 | 13,483 | Jason Bere | Pedro Martinez | Pedro Martinez | Jason Bere | | 354 | 417 | -63 |
| 1998-06-17 | vs BOS | 70 | L 5-12 | 29-41 | 3 | 13,563 | Scott Eyre | Tim Wakefield | Tim Wakefield | Scott Eyre | Tom Gordon | 359 | 429 | -70 |
| 1998-06-18 | vs MIN | 71 | L 1-4 | 29-42 | 3 | 13,550 | Mike Sirotka | Bob Tewksbury | Bob Tewksbury | Mike Sirotka | | 360 | 433 | -73 |
| 1998-06-19 | vs MIN | 72 | L 6-10 | 29-43 | 4 | 18,905 | Jaime Navarro | LaTroy Hawkins | Mike Trombley | Jaime Navarro | Greg Swindell | 366 | 443 | -77 |
| 1998-06-20 | vs MIN | 73 | W 8-7 | 30-43 | 3 | 19,823 | James Baldwin | Brad Radke | Bill Simas | Rick Aguilera | | 374 | 450 | -76 |
| 1998-06-21 | vs MIN | 74 | L 1-6 | 30-44 | 4 | 15,926 | Jason Bere | Mike Morgan | Mike Morgan | Jason Bere | Hector Carrasco | 375 | 456 | -81 |
| 1998-06-22 | @ PIT | 75 | W 5-4 | 31-44 | 4 | 21,531 | Tom Fordham | Francisco Cordova | Carlos Castillo | Elmer Dessens | Matt Karchner | 380 | 460 | -80 |
| 1998-06-23 | @ PIT | 76 | W 5-4 | 32-44 | 4 | 20,310 | Mike Sirotka | Jason Schmidt | Mike Sirotka | Jason Schmidt | Matt Karchner | 385 | 464 | -79 |
| 1998-06-24 | vs CIN | 77 | W 4-2 | 33-44 | 3 | 16,344 | Jaime Navarro | Scott Winchester | Jaime Navarro | Scott Winchester | Bill Simas | 389 | 466 | -77 |
| 1998-06-25 | vs CIN | 78 | L 5-7 | 33-45 | 4 | 14,081 | Jim Parque | Brett Tomko | Brett Tomko | Jim Parque | Jeff Shaw | 394 | 473 | -79 |
| 1998-06-26 | vs MIL | 79 | L 1-2 | 33-46 | 4 | 17,298 | James Baldwin | Jeff Juden | Jeff Juden | Bill Simas | Bob Wickman | 395 | 475 | -80 |
| 1998-06-27 | vs MIL | 80 | L 5-10 | 33-47 | 4 | 22,100 | Tom Fordham | Brad Woodall | Brad Woodall | Tom Fordham | | 400 | 485 | -85 |
| 1998-06-28 | vs MIL | 81 | W 10-8 | 34-47 | 4 | 17,455 | Mike Sirotka | Scott Karl | Bill Simas | Mike Myers | | 410 | 493 | -83 |
| 1998-06-30 | @ HOU | 82 | L 2-17 | 34-48 | 4 | 26,400 | Jaime Navarro | Sean Bergman | Sean Bergman | Jaime Navarro | | 412 | 510 | -98 |
| 1998-07-01 | @ HOU | 83 | L 4-10 | 34-49 | 4 | 29,050 | Jim Parque | Pete Schourek | Pete Schourek | Jim Parque | | 416 | 520 | -104 |
| 1998-07-02 | @ HOU | 84 | W 4-3 | 35-49 | 4 | 25,344 | James Baldwin | Jose Lima | James Baldwin | Jose Lima | Bill Simas | 420 | 523 | -103 |
| 1998-07-03 | @ BOS | 85 | L 2-15 | 35-50 | 4 | 32,467 | Mike Sirotka | Tim Wakefield | Tim Wakefield | Mike Sirotka | | 422 | 538 | -116 |
| 1998-07-04 | @ BOS | 86 | W 3-0 | 36-50 | 4 | 29,600 | John Snyder | Jin Ho Cho | John Snyder | Jin Ho Cho | Bill Simas | 425 | 538 | -113 |
| 1998-07-05 | @ BOS | 87 | L 14-15 | 36-51 | 4 | 32,970 | Jaime Navarro | Steve Avery | Carlos Reyes | Bob Howry | Tom Gordon | 439 | 553 | -114 |
| 1998-07-09 | vs KCA | 88 | L 4-6 | 36-52 | 5 | 15,023 | Mike Sirotka | Tim Belcher | Tim Belcher | Mike Sirotka | Jeff Montgomery | 443 | 559 | -116 |
| 1998-07-10 | vs KCA | 89 | W 10-3 | 37-52 | 5 | 15,378 | Jaime Navarro | Jose Rosado | Jaime Navarro | Jose Rosado | | 453 | 562 | -109 |
| 1998-07-11 | vs KCA | 90 | W 4-3 | 38-52 | 5 | 21,814 | James Baldwin | Pat Rapp | James Baldwin | Pat Rapp | Matt Karchner | 457 | 565 | -108 |
| 1998-07-12 | vs KCA | 91 | L 3-4 | 38-53 | 5 | 32,929 | Jim Parque | Glendon Rusch | Scott Service | Matt Karchner | Jeff Montgomery | 460 | 569 | -109 |
| 1998-07-13 | vs MIN | 92 | W 5-2 | 39-53 | 4 | 16,741 | John Snyder | Dan Serafini | John Snyder | Dan Serafini | Bill Simas | 465 | 571 | -106 |
| 1998-07-14 | vs MIN | 93 | W 8-5 | 40-53 | 4 | 13,841 | Mike Sirotka | Bob Tewksbury | Keith Foulke | Rick Aguilera | | 473 | 576 | -103 |
| 1998-07-15 | vs TOR | 94 | W 9-3 | 42-53 | 4 | 0 | Jaime Navarro | Pat Hentgen | Jaime Navarro | Pat Hentgen | | 482 | 579 | -97 |
| 1998-07-15 | vs TOR | 95 | W 5-2 | 42-53 | 4 | 15,602 | Carlos Castillo | Dave Stieb | Carlos Castillo | Dave Stieb | Bill Simas | 487 | 581 | -94 |
| 1998-07-16 | vs TOR | 96 | L 2-5 | 42-54 | 4 | 19,638 | James Baldwin | Chris Carpenter | Chris Carpenter | James Baldwin | Randy Myers | 489 | 586 | -97 |
| 1998-07-17 | vs CLE | 97 | W 4-3 | 43-54 | 3 | 27,733 | Jim Parque | Charles Nagy | Bill Simas | Paul Shuey | | 493 | 589 | -96 |
| 1998-07-18 | vs CLE | 98 | L 9-15 | 43-55 | 3 | 26,067 | John Snyder | Jaret Wright | Paul Shuey | Matt Karchner | Michael Jackson | 502 | 604 | -102 |
| 1998-07-19 | vs CLE | 99 | W 8-1 | 44-55 | 3 | 23,543 | Mike Sirotka | Dave Burba | Mike Sirotka | Dave Burba | | 510 | 605 | -95 |
| 1998-07-20 | vs CLE | 100 | L 4-5 | 44-56 | 4 | 27,160 | Jaime Navarro | Bartolo Colon | Bartolo Colon | Jaime Navarro | Michael Jackson | 514 | 610 | -96 |
| 1998-07-21 | @ TOR | 101 | W 6-3 | 45-56 | 3 | 30,209 | James Baldwin | Pat Hentgen | James Baldwin | Pat Hentgen | Bill Simas | 520 | 613 | -93 |
| 1998-07-22 | @ TOR | 102 | L 0-4 | 45-57 | 4 | 29,221 | Jim Parque | Roger Clemens | Roger Clemens | Jim Parque | | 520 | 617 | -97 |
| 1998-07-24 | @ NYA | 103 | L 4-5 | 45-58 | 4 | 44,264 | John Snyder | Andy Pettitte | Andy Pettitte | Bryan Ward | Mariano Rivera | 524 | 622 | -98 |
| 1998-07-25 | @ NYA | 104 | W 6-2 | 46-58 | 3 | 55,638 | Mike Sirotka | Hideki Irabu | Mike Sirotka | Hideki Irabu | Bill Simas | 530 | 624 | -94 |
| 1998-07-26 | @ NYA | 105 | L 3-6 | 46-59 | 4 | 51,865 | Jaime Navarro | David Wells | David Wells | Jaime Navarro | Mariano Rivera | 533 | 630 | -97 |
| 1998-07-28 | vs TBA | 106 | W 4-1 | 47-59 | 3 | 18,402 | James Baldwin | Rolando Arrojo | James Baldwin | Rolando Arrojo | Bill Simas | 537 | 631 | -94 |
| 1998-07-29 | vs TBA | 107 | L 2-7 | 47-60 | 3 | 17,387 | Jim Parque | Tony Saunders | Tony Saunders | Jim Parque | | 539 | 638 | -99 |
| 1998-07-31 | @ TEX | 108 | W 10-2 | 48-60 | 3 | 38,846 | John Snyder | John Burkett | John Snyder | John Burkett | | 549 | 640 | -91 |
| 1998-08-01 | @ TEX | 109 | L 1-8 | 48-61 | 4 | 42,425 | Mike Sirotka | Rick Helling | Rick Helling | Mike Sirotka | | 550 | 648 | -98 |
| 1998-08-02 | @ TEX | 110 | L 3-12 | 48-62 | 4 | 28,175 | Jaime Navarro | Aaron Sele | Aaron Sele | Jaime Navarro | | 553 | 660 | -107 |
| 1998-08-03 | @ TBA | 111 | W 6-1 | 49-62 | 4 | 24,698 | James Baldwin | Rolando Arrojo | James Baldwin | Rolando Arrojo | | 559 | 661 | -102 |
| 1998-08-04 | @ TBA | 112 | W 8-6 | 50-62 | 4 | 24,866 | Jim Parque | Tony Saunders | Carlos Castillo | Tony Saunders | Bill Simas | 567 | 667 | -100 |
| 1998-08-05 | @ TBA | 113 | L 3-7 | 50-63 | 4 | 24,814 | John Snyder | Julio Santana | Roberto Hernandez | Bob Howry | | 570 | 674 | -104 |
| 1998-08-08 | vs ANA | 114 | W 7-5 | 52-63 | 2 | 0 | Mike Sirotka | Jason Dickson | Mike Sirotka | Jason Dickson | Bill Simas | 577 | 679 | -102 |
| 1998-08-08 | vs ANA | 115 | W 4-3 | 52-63 | 2 | 24,073 | Jaime Navarro | Steve Sparks | Chad Bradford | Shigetoshi Hasegawa | | 581 | 682 | -101 |
| 1998-08-09 | vs ANA | 116 | L 0-9 | 52-64 | 3 | 16,805 | James Baldwin | Chuck Finley | Chuck Finley | James Baldwin | | 581 | 691 | -110 |
| 1998-08-10 | vs OAK | 117 | W 5-3 | 53-64 | 2 | 18,712 | Jim Parque | Kenny Rogers | Jim Parque | Kenny Rogers | Bill Simas | 586 | 694 | -108 |
| 1998-08-11 | vs OAK | 118 | L 4-6 | 53-65 | 2 | 17,095 | John Snyder | Tom Candiotti | Tom Candiotti | John Snyder | Billy Taylor | 590 | 700 | -110 |
| 1998-08-12 | vs OAK | 119 | W 2-0 | 54-65 | 2 | 15,503 | Scott Eyre | Jimmy Haynes | Scott Eyre | Jimmy Haynes | Bill Simas | 592 | 700 | -108 |
| 1998-08-14 | vs SEA | 120 | W 14-2 | 55-65 | 2 | 22,713 | Mike Sirotka | Ken Cloude | Mike Sirotka | Ken Cloude | | 606 | 702 | -96 |
| 1998-08-15 | vs SEA | 121 | L 7-13 | 55-66 | 2 | 21,537 | Jaime Navarro | Bill Swift | Bill Swift | Jaime Navarro | | 613 | 715 | -102 |
| 1998-08-16 | vs SEA | 122 | W 5-3 | 56-66 | 2 | 25,471 | James Baldwin | Jeff Fassero | Keith Foulke | Jeff Fassero | Bill Simas | 618 | 718 | -100 |
| 1998-08-17 | @ ANA | 123 | L 2-7 | 56-67 | 2 | 22,174 | Jim Parque | Steve Sparks | Steve Sparks | Jim Parque | | 620 | 725 | -105 |
| 1998-08-18 | @ ANA | 124 | W 4-3 | 57-67 | 2 | 26,160 | John Snyder | Chuck Finley | John Snyder | Chuck Finley | Bill Simas | 624 | 728 | -104 |
| 1998-08-19 | @ OAK | 125 | L 0-6 | 57-68 | 2 | 12,605 | Mike Sirotka | Blake Stein | Blake Stein | Mike Sirotka | | 624 | 734 | -110 |
| 1998-08-20 | @ OAK | 126 | L 1-3 | 57-69 | 2 | 8,607 | Tom Fordham | Kenny Rogers | Kenny Rogers | Tom Fordham | Billy Taylor | 625 | 737 | -112 |
| 1998-08-21 | @ SEA | 127 | L 4-5 | 57-70 | 2 | 34,421 | Scott Eyre | Jeff Fassero | Jose Paniagua | Keith Foulke | Mike Timlin | 629 | 742 | -113 |
| 1998-08-22 | @ SEA | 128 | L 4-5 | 57-71 | 3 | 43,596 | Jim Parque | Jamie Moyer | Mike Timlin | Jaime Navarro | | 633 | 747 | -114 |
| 1998-08-23 | @ SEA | 129 | L 2-3 | 57-72 | 3 | 35,159 | John Snyder | Paul Spoljaric | Paul Spoljaric | John Snyder | Jose Paniagua | 635 | 750 | -115 |
| 1998-08-24 | @ SEA | 130 | L 10-11 | 57-73 | 4 | 27,087 | Mike Sirotka | Ken Cloude | Ken Cloude | Mike Sirotka | Mike Timlin | 645 | 761 | -116 |
| 1998-08-25 | vs BAL | 131 | W 6-4 | 58-73 | 4 | 15,776 | Tom Fordham | Mike Mussina | Chad Bradford | Mike Mussina | | 651 | 765 | -114 |
| 1998-08-26 | vs BAL | 132 | W 12-5 | 59-73 | 4 | 13,511 | James Baldwin | Juan Guzman | James Baldwin | Juan Guzman | | 663 | 770 | -107 |
| 1998-08-27 | vs BAL | 133 | W 7-4 | 60-73 | 3 | 14,241 | Jim Parque | Scott Erickson | Jim Parque | Scott Erickson | Bill Simas | 670 | 774 | -104 |
| 1998-08-28 | vs TEX | 134 | L 5-6 | 61-74 | 3 | 0 | John Snyder | Rick Helling | Xavier Hernandez | Bob Howry | John Wetteland | 675 | 780 | -105 |
| 1998-08-28 | vs TEX | 135 | W 8-7 | 61-74 | 3 | 14,280 | Scott Eyre | John Burkett | Bryan Ward | Eric Gunderson | Bob Howry | 683 | 787 | -104 |
| 1998-08-29 | vs TEX | 136 | L 3-5 | 61-75 | 3 | 16,424 | Mike Sirotka | Aaron Sele | Aaron Sele | Mike Sirotka | John Wetteland | 686 | 792 | -106 |
| 1998-08-30 | vs TEX | 137 | W 5-3 | 62-75 | 3 | 16,701 | Tom Fordham | Todd Stottlemyre | Carlos Castillo | Todd Stottlemyre | Bob Howry | 691 | 795 | -104 |
| 1998-08-31 | @ BAL | 138 | W 4-1 | 63-75 | 3 | 40,056 | James Baldwin | Scott Erickson | James Baldwin | Scott Erickson | Bob Howry | 695 | 796 | -101 |
| 1998-09-01 | @ BAL | 139 | W 9-5 | 64-75 | 3 | 40,016 | Jim Parque | Doug Drabek | Jim Parque | Doug Drabek | Jaime Navarro | 704 | 801 | -97 |
| 1998-09-02 | @ BAL | 140 | W 3-2 | 65-75 | 2 | 46,123 | John Snyder | Sidney Ponson | John Snyder | Alan Mills | Bob Howry | 707 | 803 | -96 |
| 1998-09-04 | vs NYA | 141 | L 6-11 | 65-76 | 3 | 19,876 | Mike Sirotka | Orlando Hernandez | Graeme Lloyd | Chad Bradford | | 713 | 814 | -101 |
| 1998-09-05 | vs NYA | 142 | W 9-5 | 66-76 | 2 | 33,092 | Jim Abbott | Andy Pettitte | Jim Abbott | Andy Pettitte | | 722 | 819 | -97 |
| 1998-09-06 | vs NYA | 143 | W 6-5 | 67-76 | 2 | 24,498 | James Baldwin | Hideki Irabu | James Baldwin | Hideki Irabu | Bob Howry | 728 | 824 | -96 |
| 1998-09-07 | vs DET | 144 | W 7-5 | 68-76 | 2 | 12,978 | Jim Parque | Brian Moehler | Jim Parque | Brian Moehler | Chad Bradford | 735 | 829 | -94 |
| 1998-09-08 | vs DET | 145 | W 12-6 | 69-76 | 2 | 11,550 | John Snyder | Justin Thompson | John Snyder | Justin Thompson | | 747 | 835 | -88 |
| 1998-09-09 | vs DET | 146 | L 6-8 | 69-77 | 2 | 12,872 | Mike Sirotka | Seth Greisinger | Seth Greisinger | Mike Sirotka | | 753 | 843 | -90 |
| 1998-09-11 | @ CLE | 147 | W 3-2 | 70-77 | 2 | 43,210 | Jim Abbott | Charles Nagy | Jim Abbott | Charles Nagy | Bob Howry | 756 | 845 | -89 |
| 1998-09-12 | @ CLE | 148 | W 6-4 | 71-77 | 2 | 43,170 | James Baldwin | Dave Burba | James Baldwin | Paul Shuey | Bob Howry | 762 | 849 | -87 |
| 1998-09-13 | @ CLE | 149 | L 3-6 | 71-78 | 2 | 43,178 | Jim Parque | Jaret Wright | Paul Shuey | Bryan Ward | Michael Jackson | 765 | 855 | -90 |
| 1998-09-14 | @ DET | 150 | W 17-16 | 72-78 | 2 | 10,687 | John Snyder | Justin Thompson | Scott Eyre | Doug Bochtler | | 782 | 871 | -89 |
| 1998-09-15 | @ DET | 151 | L 0-2 | 72-79 | 2 | 10,177 | Mike Sirotka | Seth Greisinger | Seth Greisinger | Mike Sirotka | Todd Jones | 782 | 873 | -91 |
| 1998-09-16 | vs KCA | 152 | W 9-4 | 73-79 | 2 | 12,894 | Jim Abbott | Brian Barber | Jim Abbott | Brian Bevil | | 791 | 877 | -86 |
| 1998-09-17 | vs KCA | 153 | L 4-13 | 73-80 | 2 | 13,552 | James Baldwin | Tim Belcher | Tim Belcher | James Baldwin | | 795 | 890 | -95 |
| 1998-09-18 | vs BOS | 154 | W 11-9 | 74-80 | 2 | 17,767 | Jim Parque | Steve Avery | Jim Parque | Steve Avery | Bill Simas | 806 | 899 | -93 |
| 1998-09-19 | vs BOS | 155 | W 5-2 | 75-80 | 2 | 21,924 | John Snyder | Pedro Martinez | John Snyder | Pedro Martinez | | 811 | 901 | -90 |
| 1998-09-20 | vs BOS | 156 | W 6-4 | 76-80 | 2 | 24,165 | Mike Sirotka | Tim Wakefield | Mike Sirotka | Jim Corsi | Bryan Ward | 817 | 905 | -88 |
| 1998-09-21 | @ MIN | 157 | W 7-1 | 77-80 | 2 | 6,862 | Jim Abbott | Bob Tewksbury | Jim Abbott | Bob Tewksbury | | 824 | 906 | -82 |
| 1998-09-22 | @ MIN | 158 | W 4-1 | 78-80 | 2 | 7,313 | James Baldwin | Eric Milton | James Baldwin | Eric Milton | | 828 | 907 | -79 |
| 1998-09-23 | @ MIN | 159 | L 6-7 | 78-81 | 2 | 6,765 | Jim Parque | LaTroy Hawkins | Mike Trombley | Scott Eyre | | 834 | 914 | -80 |
| 1998-09-24 | @ KCA | 160 | L 4-6 | 78-82 | 2 | 13,481 | Jaime Navarro | Jose Rosado | Jose Rosado | Jaime Navarro | Jeff Montgomery | 838 | 920 | -82 |
| 1998-09-25 | @ KCA | 161 | W 3-0 | 79-82 | 2 | 16,683 | Mike Sirotka | Jeff Suppan | Mike Sirotka | Ricky Bones | Bob Howry | 841 | 920 | -79 |
| 1998-09-26 | @ KCA | 162 | W 13-5 | 80-82 | 2 | 21,846 | Jim Abbott | Brian Barber | Jim Abbott | Brian Barber | | 854 | 925 | -71 |
| 1998-09-27 | @ KCA | 163 | W 7-6 | 81-82 | 2 | 13,578 | James Baldwin | Tim Belcher | James Baldwin | Tim Belcher | Bob Howry | 861 | 931 | -70 |