McEwan graduated from George Brown College in 1979. In 1981, McEwan was hired by the Sutton Place Hotel in Toronto as executive sous chef. Two years later he was promoted to chef. He opened his first restaurant, North 44, in 1990. In August 2007, McEwan opened ONE at The Hazelton Hotel, Toronto's only 5-star hotel. In June 2009, McEwan opened his first grocery store at the Shops at Don Mills. "McEwan" is promoted as an upscale grocery store. McEwan's first book, Great Food at Home, was published in early 2011. Since 1990, Mark has been an Ambassador for Second Harvest in Toronto, helping to spread the word about food rescue and hunger relief.