Born and raised in the Toronto suburb of Scarborough, Ontario, Mike Sullivan played hockey within the Greater Toronto Area until 2011, when he began a collegiate career at Bowling Green State University. After playing 4 years for the Falcons, he graduated and joined his older brother in Italy, signing with Asiago in the Italian Professional Hockey League. After 2 seasons in Italy, and 1 remaining on his contract, he began pursuing a career in officiating by applying to the 2017 NHL Officiating Amateur Exposure Combine. After an eye opening week at the combine, he returned to Italy for another season, where his team won the Alps Hockey League Championship, and he got the esteemed privilege of representing Italy at the 2018 World Championships. That summer, he attended the 2018 NHL Officiating Combine once again, to continue to develop as a potential official. He played one final season in the UK’s Elite League, where he played for the Scottish based Dundee Stars, while also earning his Master’s Degree in Business from the University of Dundee.
After once again attending the 2019 NHL Officiating Combine, he picked up a whistle and began his officiating career, working 200 youth games in the Greater Toronto Hockey League (GTHL), while also being a linesperson for the Ontario Hockey League (OHL), and a Referee for the American Hockey League (AHL). He transitioned to full time Referee in the AHL for the 2021 season, working a full schedule including the first two rounds of the Calder Cup Playoffs. The 2022-23 season was his 4th AHL season, where he continued to hone his game through a full season schedule, earning the honor of working the Calder Cup Conference Finals. After that season, In June of 2023, his on-ice career would come full circle, as he would be offered a minor league referee NHL contract in his hometown of Toronto.