Gascon is the first judge since 2006 to join the panel without appearing before an ad hoc committee of parliamentarians.
He fills a vacancy that's been open for more than a year, the longest in the court's history.
In often light-hearted remarks at a ceremony welcoming him to the bench, Gascon thanked the court and Chief Justice Beverley McLachlin, adding he thought about taking a selfie to commemorate the event "but the judiciary is not there yet."
A self-described workaholic, he also said his wife had joked that appointing him to the Supreme Court was "like appointing an alcoholic the president of the LCBO." The LCBO is the Liquor Control Board of Ontario.
In more sombre comments, the 54-year-old Gascon said he takes on his new job with a mix of "pride and apprehension," adding he feels blessed to serve as a Supreme Court justice.
"I want to make sure I am worthy of the trust placed in me," he said.
"I intend to live up to the challenge to the best of my abilities. Like all the members of the court, I want to maintain the essential trust of Canadians in their judiciary. I hope I'll be able to make the justice system more effective, more intelligible, more accessible to my fellow Canadians."
McLachlin described Gascon as a "hard-working and gifted jurist."
Gascon joins the bench with a number of hot-button cases on the horizon, touching on issues such as assisted suicide and the gun registry.
Prime Minister Stephen Harper named Gascon to the Supreme Court in June after the court ruled his previous selection, Federal Court Justice Marc Nadon, was ineligible. The Nadon affair touched off an unprecedented public spat between the Conservatives and McLachlin.
As a result, Justice Minister Peter MacKay said Gascon would not be required to appear before the parliamentary committee, a normal part of the appointment process, because that process is now under review.
Harper selected Gascon without public hearings or the use of a five-person panel — made up of three government MPs and two opposition MPs — to select a short list of potential candidates.
MacKay was on hand for Monday's ceremony, congratulating Gascon "for an honour well-deserved."
Gascon is a Montrealer and an expert in commercial law. He is a McGill graduate who was called to the Quebec bar in 1982. He was named to the Quebec Superior Court in 2002 and joined the Quebec Court of Appeal in April 2012.
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Note to readers: This is a corrected story. An earlier version said Gascon is the first judge appointed to the court in a decade
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