The 38-year-old will provide cover for Thibaut Courtois and Willy Caballero in Maurizio Sarri's first season in charge of the Blues.
Green, who was on Huddersfield Town's books last season but failed to play a single minute of action, has penned a one-year deal at Stamford Bridge.
Speaking about the move, Green told Chelsea's official club website: “It has been a whirlwind 24 hours.
“You are thinking about your career and where you want to go and then you get a phone call like this, and it is a short conversation.
“It has been a pretty dramatic time for me and I can’t wait to get started. I am absolutely delighted and it is a thrill and an honour to be here.”
Chelsea FC has today completed the signing of Rob Green, who joins to provide backup for Thibaut Courtois and Willy Caballero... https://t.co/EzkhZxBHu6— Chelsea FC (@ChelseaFC) July 26, 2018
Green has also represented England at two major international tournaments in the past.
He becomes Chelsea's second signing of the summer following the earlier arrival of Jorginho from Napoli in a £57million ($86m) deal.