Steve Mason was born on May 29, 1988 in Oakville, Ontario. After playing just 12 games in his rookie year in the OHL, he was selected by the Columbus Blue Jackets in the 3rd round, 69th overall, in the 2006 NHL Entry Draft.
Mason started the 2007-08 NHL season with the Columbus Blue Jackets but was returned to London after being a healthy scratch for Columbus' first two games of the season. While competing for Team Canada at the 2008 World Junior Championships, he was traded by the London Knights to the Kitchener Rangers on January 4, 2008, hours before the semi-final game.
Approaching his first professional season, Mason underwent knee surgery in September, causing him to miss the first month of play in the AHL with the Blue Jackets' minor league affiliate, the Syracuse Crunch. Shortly after joining the Crunch's lineup, Mason was called up by the Blue Jackets on November 4, 2008 due to the injury of starter Pascal Leclaire. He made his NHL debut the next night, defeating, the Edmonton Oilers 5-4. Mason continued to start games upon Leclaire's return from injury and was named NHL rookie of the month for November.
Mason won the 2009 Calder Memorial Trophy as rookie of the year and was also nominated for the Vezina Trophy as the NHL's top goaltender, though the award would go to Tim Thomas of the Boston Bruins.
Mason would struggle to during 2009-10 to find the form that just one year earlier had made him one of the top goaltenders in the NHL. He struggled further during the 2011-12 season, with his save percentage dropping to .894 and his goals against average inflating to 3.39.
On April 3, 2013, the NHL's trade deadline, Mason's time in Columbus would come to an end. He was shipped to the Philadelphia Flyers in exchange for fellow goaltender Micheal Leighton.