List of Portuguese football transfers winter 2009–10

This is a list of Portuguese winter football transfers for the 2009–10 season.

The winter transfer window opened on 1 January 2010 and closed on 31 January 2010.

Players could be bought before the transfer window opened, but were not permitted to join their new clubs until 1 January.

Additionally, players without a club could join at any time and clubs were able to sign a goalkeeper on an emergency loan if they had no registered goalkeeper available.

Only moves involving Primeira Liga clubs are listed; included are clubs that completed transfers after the end of the summer 2009 transfer window and before the end of the 2009–10 winter window.