The announcement was made Tuesday by Keith Cox, executive vice president of development and original programming for the cable network.
"The show is a force in and of itself, so it's a no-brainer to renew it again," Cox said in a statement. "Critics and fans love it, and I know [creator] Darren [Starr] and the entire cast and crew behind Younger will continue to deliver at the top of their game."
Co-starring Miriam Shor, Nico Tortorella, Peter Hermann and Molly Bernard, the show began production on its third season this week in New York.
Season 3 of Younger is scheduled to premiere Sept. 28. The series follows Foster's character Liza, "a 40-year old woman who pretends to be 26 in order to get a job in the highly competitive world of publishing -- and succeeds," a synopsis said.