The actor and singer will join the BBC soap for a short stint as newcomer Luke, and will film his first scenes this week.
Luke is described as an ambitious young man who is deeply in love with Stacey (Lacey Turner). He is working hard in the city, determined to build a secure life for himself and his family.
But Stacey hasn't been entirely honest with Luke since they became romantically involved – and it won't be plain sailing for the new couple.
"I am so thrilled to be a part of such an iconic show," Matt said. "I grew up watching EastEnders so this is really exciting to me!"
EastEnders executive producer Dominic Treadwell-Collins said of the casting, "I've always loved Matt and it will be a real treat for viewers to watch him and Lacey get together on screen as part of her return to the Square.
"Luke gives as good as good as he gets, so is a great foil to Stacey. Pity she's been lying to him since the day she met him…"
It was recently announced that Lacey is reprising her role as Stacey after three years away from the show. The character was last seen fleeing the country after she was exposed as the killer of Archie Mitchell.
Matt, 30, meanwhile, is best known for being in the pop band Busted, who recently merged with McFly to form supergroup McBusted.
His acting credits include Miss Marple and Casualty and he appeared on stage in Wicked and Footloose. Next year, he will star in the revival of the hit sitcom Birds of a Feather.