The 32-year-old, who last played in England for Cardiff City in 2013, has recently left Toronto FC.
He has been training with the Tangerines this week, and manager Barry Ferguson has now offered him a deal until the end of the season in the hope that Earnshaw's goals will help fire them to Championship safety.
Earnshaw has netted 16 times in 58 appearances for his country, and his previous clubs include Norwich City, West Bromwich Albion and Nottingham Forest and Israeli outfit Maccabi Tel Aviv.
"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," he told the club'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 are currently six points above the drop zone and face Huddersfield on Saturday, but Earnshaw will not be available until the midweek match with Bolton Wanderers as he awaits international clearance.