Kathleen Turner is set to join Jim Carrey and Jeff Daniels in Dumb And Dumber To.
The Californication star will play their love interest in the comedy sequel, which will be directed again by brothers Bobby and Peter Farrelly.
The news was confirmed by Peter, who tweeted: "Kathleen Turner is officially in Dumb an Dumber To. She plays Fraida Felcher - the legendary hose-hound from Cranston! #dumbto"
Jim and Jeff have already signed on to reprise their roles as hapless and dim-witted best friends Lloyd Christmas and Harry Dunne.
Peter also revealed that Brady Bluhm will return to play the pair's blind neighbour Billy in the upcoming instalment.
"It's official! Billy in 4C (I just thought he was really quiet) is returning in #DumbTo! Played again by the highly underrated Brady Bluhm," he wrote.
Dumb And Dumber To, which has been co-written by the Farrelly brothers and Bennet Yellin, who all teamed up to write the first movie, and The Stooges' Mike Cerrone, is due to start shooting in mid-September.
It is expected to be released in summer 2014, to coincide with the first film's 20th anniversary.