It will be the third time Westbrook has starred in the soap
Former EastEnder Danniella Westbrook is set to return to the BBC One soap as Sam Mitchell this summer.
"I'm really happy to be coming back, it feels just like coming home," the actress said.
Westbrook, 35, first appeared on Albert Square in 1990 but left in 1996. She spent a brief second stint in the show between 1999 and 2000.
In 2002, she was replaced in the role by another actress, Kim Medcalf, who left EastEnders in 2005.
Sam Mitchell was last seen on screen, making a quick exit to Brazil after becoming a suspect in the Dirty Den murder case.
The soap's executive producer, Diederick Santer, paid tribute to Medcalf, seen recently in ITV medical drama Harley Street.
Westbrook's character Sam married Ricky, played by Sid Owen
"I'd like to take this opportunity to thank Kim Medcalf for her great work playing Sam Mitchell for three years and welcome Danniella back to pick up the baton once again."
Westbrook, a self-confessed former cocaine addict, took part in I'm A Celebrity... Get Me Out of Here! in 2003 but left because she was worried it was affecting her recovery from drug addiction.
"I can't wait to get the scripts to see what Sam Mitchell has been up to since she was last in the Square," said Westbrook.