Ava (Clare Perkins) - the long-lost daughter of show regular Cora Cross - makes her first appearance on screen on November 20, while Dexter will join her in Walford in 2013.
Hot on the heels of his mum, 20-year-old Dexter turns up on the Square in search of some answers and to get to meet the family he never knew he had.
Actor Khali Best has landed the role of Dexter and will be a new regular cast member for the BBC soap.
Pictured: New cast members Khali Best and Clare Perkins.
Best told Digital Spy: "I am delighted to be joining the cast of EastEnders and working with such great actors so early in my career is an amazing opportunity. I am really excited to see what the writers have in store."
EastEnders' executive producer Lorraine Newman added: "Dexter is a force of nature: cheeky, forthright, confident but highly protective of his mum and vice versa. He'll work at the Arches and be a great mate for Jay and Lola. I am sure he'll be hugely popular with the audience."
Dexter Hartman's first scenes will air in January 2013.