| Hank Aaron | ATL, ML1, ML4 | 1B, 2B, 3B, CF, DH, LF, OF, RF |
| Tommie Aaron | ATL, ML1 | 1B, 2B, 3B, CF, LF, OF, RF |
| Don Aase | BAL, BOS, CAL, LAN, NYN | P |
| Andy Abad | BOS, OAK | 1B, OF, RF |
| John Abadie | BR2, PH3 | 1B |
| Ed Abbaticchio | BSN, PHI, PIT | 2B, 3B, OF, SS |
| Bert Abbey | BRO, CHN, WSN | P |
| Charlie Abbey | WSN | OF, P |
| Dan Abbott | TL2 | P |
| Fred Abbott | CLE, PHI | 1B, C |
| Glenn Abbott | DET, OAK, SEA | P |
| Jeff Abbott | CHA, FLO | CF, DH, LF, OF, RF |
| Jim Abbott | CAL, CHA, MIL, NYA | P |
| Kurt Abbott | ATL, COL, FLO, NYN, OAK | 1B, 2B, 3B, CF, DH, LF, OF, RF, SS |
| Kyle Abbott | CAL, PHI | P |
| Ody Abbott | SLN | OF |
| Paul Abbott | CLE, KCA, MIN, PHI, SEA, TBA | P |
| Al Aber | CLE, DET, KC1 | P |
| Francis Abercrombie | TRO | SS |
| Bill Abernathie | CLE | P |
| Brent Abernathy | KCA, MIN, TBA | 2B, DH, LF, OF |
| Tal Abernathy | PHA | P |
| Ted Abernathy | ATL, CHN, CIN, CLE, KCA, SLN, WS1 | P |
| Woody Abernathy | NY1 | P |
| Cliff Aberson | CHN | OF |
| Harry Ables | CLE, NYA, SLA | P |
| Shawn Abner | CAL, CHA, SDN | CF, DH, LF, OF, RF |
| Cal Abrams | BAL, BRO, CHA, CIN, PIT | 1B, CF, LF, OF, RF |
| George Abrams | CIN | P |
| Johnny Abrego | CHN | P |
| Bobby Abreu | HOU, LAA, NYA, PHI | CF, DH, LF, OF, RF |
| Joe Abreu | CIN | 2B, 3B |
| Bill Abstein | PIT, SLA | 1B, 2B, OF |
| Jose Acevedo | CIN, COL | P |
| Juan Acevedo | COL, DET, FLO, MIL, NYA, NYN, SLN, TOR | P |
| Jim Acker | ATL, SEA, TOR | P |
| Tom Acker | CIN | P |
| Fritz Ackley | CHA | P |
| Cy Acosta | CHA, PHI | P |
| Ed Acosta | PIT, SDN | P |
| Jose Acosta | CHA, WS1 | P |
| Merito Acosta | PHA, WS1 | OF |
| Mark Acre | OAK | P |
| Jerry Adair | BAL, BOS, CHA, KCA | 1B, 2B, 3B, SS |
| Jimmy Adair | CHN | SS |
| Ace Adams | NY1 | P |
| Babe Adams | PIT, SLN | P |
| Bert Adams | CLE, PHI | 1B, C |
| Bob Adams | BOS | P |
| Bob Adams | PHI | P |