Desharnais parlayed a solid performance during the 2024 Stanley Cup Playoffs into signing a two-year, $4 million contract (average annual value of $2 million) with the Vancouver Canucks on July 1. He impressed Canucks general manager Patrik Allvin with his size and strength while helping Edmonton to a seven-game win against Vancouver in the Western Conference Second Round and to Game 7 of the Stanley Cup Final, a 2-1 loss to the Florida Panthers.

His first season with the Canucks lasted 34 games. Desharnais was traded to the Pittsburgh Penguins with Danton Heinen, Melvin Fernstrom and a first-round pick in the 2025 NHL Draft on February 1, 2025, for Marcus Pettersson and Drew O'Connor. A month later, he was traded to the San Jose Sharks.

Desharnais had an assist with 22 penalty minutes in 16 games of the 2024 playoffs after getting 11 points (one goal, 10 assists) with 54 penalty minutes and a plus-3 rating in 78 regular-season games. The native of Laval, Quebec, was chosen by the Oilers in the seventh round (No. 183) of the 2016 NHL Draft.

He played for Wichita of the ECHL and Bakersfield of the American Hockey League before joining the Oilers. He played his first NHL game, a 6-2 win against the Anaheim Ducks on Jan. 11, 2023, and scored his first goal in his 42nd NHL game to help Edmonton defeat the Calgary Flames 5-2 in the 2023 Heritage Classic at Commonwealth Stadium.