The 32-year-old striker has returned to England following a spell in the MLS with Toronto, and hopes to hit the ground running under caretaker Blackpool manager Barry Ferguson.
Blackpool become Earnshaw's sixth British club, with the forward having been a regular scorer for Cardiff City, West Brom, Norwich City and Nottingham Forest either side of an unproductive spell at Derby County.
"This is a great opportunity for me to play some games and give the fans something to cheer about before the end of the season," Earnshaw told Blackpool's official website.
"Mentally I feel really fresh because I've been dying to go, so signing here is going to be exciting.
"I'm hoping I can come here and give the fans some goals and somersaults, give them what I've given to every other team."
Blackpool have only won one of their last 19 league matches and currently sit six points clear of the Championship relegation zone with nine games to play.
