The comedic actress will arrive in Albert Square as Manda Best, who was born in Walford and returns when her only son goes to university and her marriage breaks up, The Sun reports.
Manda will start dating Phil’s friend Minty – played by Cliff Parisi – but soap fans will soon sees she still carries a torch for Phil (Steve McFadden).
A show insider said: “She returns and keeps busy by teaching night classes in art and pottery and drinking in E20. It’s not long before she bumps into familiar faces, including Phil, who she dated at school, and Minty. But are they pleased to see her?”
Josie has already begun filming and will be seen in the BBC1 soap in March.
Josie, 49, said: “I’m so excited. Everyone at EastEnders has made me feel so at home. It’s mind-boggling to walk into Albert Square after having watched the show for so many years! I can’t wait to see how my character develops on screen.”
EastEnders boss Diederick Santer said: “I’m so excited Josie’s joining us. I’ve enjoyed her brilliant comic performances for over 20 years, and can’t wait to see her in Walford.”
Josie is most famous for improvisational comedy panel show Whose Line Is It Anyway? which ended in 1998 after a 10-year TV run.
Her last TV appearance was on E4 hit Skins where she played Liz Jenkins, the estranged mother of Sid Jenkins (Mike Bailey).