The 44-year-old will join fellow celebrity chefs Monica Galetti and Gregg Wallace on the judging panel for the seventh series of the BBC2 show, which is due to be broadcast in the autumn.
Marcus, who is currently Chef Patron of a restaurant in Knightsbridge, west London, will take Michel's place after the two-star Michelin chef stepped down earlier this year.
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The parting of ways was a result of a dispute with the BBC about his endorsement of a brand of potatoes.
The new addition to the judging panel will create quite a stir, as Marcus is known for his direct and no-frills attitude while Michel is charming and gentle in approach.
Marcus spoke of his excitement at the new role: "I have been watching MasterChef since I was a young kid at catering college and in more recent years I have enjoyed an established relationship with the programme.
"To now become part of the show is hugely exciting for me; to be asked is a true honour.
"Michel has left big shoes to fill and I am delighted to be working with Monica and Gregg on a new journey of discovery to find the next generation of Michelin-starred chefs."
Marcus began his career at the age of 18 working at The Savoy, and went on to be awarded his first star seven years later.
He worked alongside famous chef Gordon Ramsay in a 15-year partnership, before the two branched out independently.