Major League Baseball invited 119 teams to join the minor leagues, beginning in 2021.
The Triple-A and Double-A affiliates who received invites are listed below. The High-A and Low-A affiliates can be found here.
American League
| TEAM | AAA | AA |
|---|---|---|
| Angels | Salt Lake | Rocket City |
| Astros | Sugar Land | Corpus Christi |
| Athletics | Las Vegas | Midland |
| Blue Jays | Buffalo | New Hampshire |
| Indians | Columbus | Akron |
| Mariners | Tacoma | Arkansas |
| Orioles | Norfolk | Bowie |
| Rangers | Round Rock | Frisco |
| Rays | Durham | Montgomery |
| Red Sox | Worcester | Portland |
| Royals | Omaha | Northwest Arkansas |
| Tigers | Toledo | Erie |
| Twins | St. Paul | Wichita |
| White Sox | Charlotte | Birmingham |
| Yankees | Scranton/Wilkes-Barre | Somerset |
National League
| TEAM | AAA | AA |
|---|---|---|
| Braves | Gwinnett | Mississippi |
| Brewers | Nashville | Biloxi |
| Cardinals | Memphis | Springfield |
| Cubs | Iowa | Tennessee |
| Diamondbacks | Reno | Amarillo |
| Dodgers | Oklahoma City | Tulsa |
| Giants | Sacramento | Richmond |
| Marlins | Jacksonville | Pensacola |
| Mets | Syracuse | Binghamton |
| Nationals | Rochester | Harrisburg |
| Padres | El Paso | San Antonio |
| Phillies | Lehigh Valley | Reading |
| Pirates | Indianapolis | Altoona |
| Reds | Louisville | Chattanooga |
| Rockies | Albuquerque | Hartford |
Initially, 120 teams were expected to receive invites, but an issue with a Rockies affiliate in Fresno remains unresolved.
The Frederick Keys will also become the sixth member of the newly-formed MLB Draft League, sources told JJ Cooper of Baseball America.
MiLB reportedly agreed to cut 42 minor-league affiliates last April after MLB commissioner Ron Manfred proposed the idea.