In the 2021 Census of Population conducted by Statistics Canada, Saint-Cyrille-de-Lessard had a population of 742 living in 385 of its 559 total private dwellings, a change of 3.3% from its 2016 population of 718. With a land area of 230.52 km2 (89.00 sq mi), it had a population density of 3.2/km2 (8.3/sq mi) in 2021.[4]