Roger Griffiths, known for his roles in Casualty, Doctors and Holby City, will play Mitch Baker for a short stint in March.
And the BBC1 soap says his arrival on the Square spells trouble for the Taylor family.
Griffiths said: “The Taylors are an established tight-knit family on the square, so coming in as Mitch – the wild card – meant I had to hit the ground running.
“I had a brilliant time and the actors who make up the Taylor family made me feel at home instantly. It was love at first sight.”
Viewers will meet Mitch next month when he turns up at The Arches, saying he happened to be in Walford when his van needed to be repaired, and it is revealed that he is Karen Taylor’s ex.
He will appear in a handful of episodes from March 12.
Roger Griffiths to appear in EastEnders as Mitch Baker