Major League Baseball assigned 24 umpires to the 2021 American and National League Division Series round of MLB's postseason, with crew chiefs Sam Holbrook and Tom Hallion in the ALDS. Ted Barrett and Alfonso Marquez head up the NLDS crews.
Crew Chiefs are indicated in bold text and by the -cc suffix with regular season crew chiefs denoted by an asterisk (*) while those working their first Division Series will be noted with a ^1st DS^ mark.
Notable regarding the ejections, tally, the Tampa Bay Rays (ALDS A) are the only team in baseball not to have experienced an ejection in 2021. This is the first time a team has gone ejection-less since Dusty Baker managed the Cincinnati Reds in 2013.
AL Division Series A (Boston Red Sox @ Tampa Bay Rays) Umpires:
HP: Dan Bellino
1B: DJ Reyburn [Game 2 Plate]
2B: Sam Holbrook* -cc [Game 3 Plate]
3B: Ron Kulpa [Game 4 Plate]
LF: Greg Gibson [Game 5 Plate]
RF: Brian Knight
AL Division Series B (Chicago White Sox @ Houston Astros) Umpires:
HP: Adam Hamari ^1st DS^
1B: Chris Conroy [Game 2 Plate]
2B: Tom Hallion* -cc [Game 3 Plate]
3B: Vic Carapazza [Game 4 Plate]
LF: Chad Fairchild [Game 5 Plate]
RF: Lance Barrett
NL Division Series A (Los Angeles Dodgers @ San Francisco Giants) Umpires:
HP: Carlos Torres ^1st DS^
1B: Angel Hernandez [Game 2 Plate]
2B: Ted Barrett* -cc [Game 3 Plate]
3B: Pat Hoberg [Game 4 Plate]
LF: Doug Eddings [Game 5 Plate]
RF: Gabe Morales ^1st DS^
NL Division Series B (Atlanta Braves @ Milwaukee Brewers) Umpires:
HP: Mike Estabrook
1B: Mike Muchlinski [Game 2 Plate]
2B: Alfonso Marquez* -cc [Game 3 Plate]
3B: Tony Randazzo [Game 4 Plate]
LF: Will Little [Game 5 Plate]
RF: Quinn Wolcott
Replay Review: Fieldin Culbreth*, CB Bucknor, Chris Guccione, Adrian Johnson.