On Wednesday evening at 8 pm ET, all 27 MLS rosters for the remainder of the 2021 season will lock through MLS Cup (December 11).

The MLS Roster Freeze Date arrives on September 15, when all clubs must submit their final 30-man roster. The only exceptions through December 11 will be cases of Extreme Hardship. The rosters will be locked until the half-day trade window on December 12, the official start of the offseason before the 2022 campaign.

Additional roster and player transaction information can be found on the 2021 MLS Roster Rules and Regulations page.

Clubs have been able to sign (mostly) free agents between the end of the Secondary Transfer Window on August 5 and the Roster Freeze Date. Among others, LAFC added goalkeeper Jamal Blackman, FC Cincinnati signed midfielder Kyle Scott, Columbus Crew inked defender Steven Moreira and CF Montréal added attacking midfielder Matko Miljevic.

MLS Decision Day is November 7, ending the 34-game regular season before the Audi 2021 MLS Cup Playoffs begin November 20. The top seven teams in each conference qualify for the postseason, with the races heating up in each conference as all clubs have between nine and 13 games remaining.