Mercer made the announcement on CBC's "The National," saying the contract was made official secretly several weeks ago.
This is the first time Mercer's show, currently in its 11th season, has inked a deal for more than a single season.
"We've only ever gone from year to year. This is a big deal for us," Mercer said. "Signing a three-year agreement is a three-year deal to do my dream job."
The deal is set to begin at the start of the 2014 season, which will be the 12th season of "Rick Mercer Report."
The head of CBC's English-language services, Heather Conway, approached Mercer with the idea to sign him for three years, instead of the traditional single season. Mercer and his producers say the extended contract allows him to look further ahead and approach next season a little differently with that in mind.
"The broadcast horizon is changing," Mercer said. "I am super lucky."
The St. John's, N.L., native debuted "Rick Mercer Report" on CBC Television in 2004. The most-watched Canadian television comedy, the show garners more than a million viewers each week.
In March 2014, he picked up two Canadian Screen Awards for Best Performance in a Variety or Sketch Comedy Program or Series and for Best Variety or Sketch Comedy Program or Series. In 2013 he won the Canadian Screen Award for Best Music, Variety, Sketch comedy or Talk Program and Best Performance in a Variety or Sketch Comedy Program.