Guillemette was drafted in the third round, 27th overall, in the 2023 CFL Draft by the Toronto Argonauts and signed with the team on May 8, 2023.[3] He won the job as the team's long snapper early in training camp in 2023, supplanting the team's incumbent, Maxime Latour, who was released on May 17, 2023.[4] Guillemette made his professional debut in the team's season opener on June 18, 2023, against the Hamilton Tiger-Cats.[5] He played in all 18 regular season games as well as the team's East Final loss to the Montreal Alouettes.[6]
In 2024, Guillemette played in 17 regular season games while sitting out one due to injury.[2] He also played in all three post-season games, including the 111th Grey Cup where the Argonauts defeated the Winnipeg Blue Bombers 41–24 and he won his first Grey Cup championship.[7]