The 23-year-old will play Dawn Bellamy, niece of the late Phil Bellamy, in ITV1’s Sixties-set drama.
She quit Coronation Street in autumn 2005 when her character Candice left Weatherfield to become a stylist for Status Quo.
Since then she has appeared in episodes of BBC dramas Holby City and New Street Law, and sung on X Factor: Battle Of The Stars.
At one point she was touted as a replacement for Billie Piper in Doctor Who, but the role eventually went to Freema Agyeman.
Nikki said: “I’m so excited about starting on Heartbeat and meeting all of the cast. My family and I have always loved the show, and I can’t wait to put on the Sixties clothing.”
She will begin filming in Yorkshire at the end of this month and appear on screen later in 2008.
Her character is sent to Aidensfield on an extended holiday because her father worries she has got in with the wrong crowd.
She gets a job in the pub but – just like Candice – dreams of a glamorous career down south.
Heartbeat producer Archie Tait said: “Nikki will be a fantastic addition to the show. Dawn is a great character who is certain to spice things up in Aidensfield.”