Keinan, who has agreed an initial one-year deal with an option for a further 12 months, has become the seventh summer recruit for Tangerines boss Ian Holloway after moving on a free transfer from Maccabi Haifa.
The 25-year-old defender has passed a medical and been granted a work permit and will go straight into the squad for Saturday's trip to London to take on Arsenal.
"I'm looking forward to the first game and I'm very happy that everything is done," Keinan told the club website.
"I just want to play for Blackpool and help this team. I had different offers but after I met the gaffer I was sure that I wanted to play for Blackpool."