Johnston has joined Wareing, who was also a judge for the BBC2 show, at his restaurant Marcus at The Berkeley Hotel in Knightsbridge, central London, as senior chef de partie.
The MasterChef winner left his role as sous chef at the Royal Oak in Maidenhead, Berkshire to take up his role at Marcus.
The Knightsbridge restaurant tweeted: “We are thrilled to announce that last year’s MasterChef winner Craig Johnston has joined our incredible team as senior chef de partie.
“We are really excited to have this hugely talented chef join us! Watch this space!”
The chef also tweeted and said: “Today is the beginning of a new chapter in my career. Senior cdp at Belgravia.”
The MasterChef official Twitter account congratulated Johnston on social media. It said: “Huge congratulations to The Professionals 2017 champion on joining the team as senior chef de partie at Marcus Wareing’s restaurant.”
Johnston, who won the Gastropub Chef of the Year at this year's Estrella Damm Top 50 Gastropubs awards, hit the headlines last year after winning MasterChef: The Professionals 2017. His cooking astounded judges on the BBC2 show, especially considering the chef’s tender age of 21 at the time.
He was the youngest champion of the prestigious cooking competition and fought off stiff competition from Louisa Ellis and Steven Lickley in the final episode to show the judges how far he could push himself.
Challenges in the competition included creating and delivering a Michelin-standard dish for 23 gastronomical giants from around the world, travelling to the south of France to learn in two Michelin-starred kitchens of the fourth best restaurant in the world – Mirazur by Argentinian chef Mauro Colegreco.
The ultimate challenge for the final three chefs was to create the best three-course meal of their lives for judges Wareing, Monica Galetti and Gregg Wallace in three hours.
Johnston’s winning menu started with torched mackerel and mackerel tartare with salt-baked beetroot, horseradish milk gel, beetroot pickled onions, garnished with beet leaves and a sorrel and dill-iced granita.
His main course was a roasted squab pigeon with thyme-infused pomme anna, a ras el hanout-spiced pigeon leg pastille, charred and roasted thyme onions with a nasturtium oil, radiccio leaves and a red pepper and tomato ketchup, finished with pigeon sauce.
The chef’s dessert was sauterne and yoghurt mousse, basil marshmallow, bergamot curd and olive oil crumble, finished with frozen lemon cells and verbena frozen rocks.