The deal is for $5.8 million -- $2.6 million in 2011-12 and $3.2 million the next season, sources told ESPN.com's Pierre LeBrun.
The Calder Trophy winner as the NHL's rookie of the year two seasons ago, Mason slumped last season as the Blue Jackets failed to return to the playoffs.
Only 22, Mason has an NHL record of 53-46-16 with a 2.65 goals-against average, a .908 save percentage and 15 shutouts in 119 games during his first two seasons.
The Oakville, Ontario, native was chosen by Columbus in the second round of the 2006 draft.
General manager Scott Howson, who announced the signing on Monday, said it was important to lock up such an important piece of the young team's future.
Information from The Associated Press was used in this report.