Kierston has landed the role of Ashley Dixon, the villain who was on the hunt for Ben Bradley's daughter Carly before she died.
The character has already been mentioned in the soap, but viewers will see Kierston make her screen debut next month.
Speaking about her new role, Kierston said: "I would describe Ashley as a control freak - I don't believe she has a nice bone in her body but I'm enjoying every minute of playing her."
"I'm also thoroughly enjoying working with Greg Wood, Jorgie Porter and Charlie Wernham among others. Their characters are just a few who get manipulated by Ashley in some way or another, so stayed tuned to see if she gets want she wants..."
Kierston played Kirsty Branning in EastEnders from 2012 to 2014. She's also starred in Glue, Inside Men and Top Boy.
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