He made 55 appearances for the Canadian national team and scored a national record 19 goals. He is also former head coach of the Canadian national team, having held the post from May 2007 until March 27, 2009.
Mitchell played every minute of Canada's matches at the 1984 Summer Olympics, scoring three goals including the equalizer that took Brazil to extra-time and eventually penalty kicks in the quarterfinals.
He made his senior debut for Canada in a September 1980 friendly match against New Zealand and played his final international in August 1993 against Australia. He represented Canada in 22 World Cup qualifiers and also played in the 1986 FIFA World Cup finals in Canada's third group stage match against Hungary.
Following his retirement as a player, Mitchell coached the 86ers reserves squad and was first-team assistant coach from 1995 to 1999, when he succeeded Carl Valentine as the club's head coach (as the club changed their name to the Vancouver Whitecaps). From 2001 to 2007, Mitchell served as Canada's Under-20 national team head coach. In 2004, he served as an assistant coach to Frank Yallop with the senior national team during FIFA World Cup Qualifiers. In May 2007, he was appointed head coach of the Canadian men's senior team. In 2008, he failed to guide Canada beyond CONCACAF Stage III of the FIFA World Cup Qualifiers, falling in the so-called CONCACAF Group of Death while higher-ranked nations Mexico and Honduras advanced to the final stage. He was relieved of his duties on 27 March 2009.