In the 2021 Census of Population conducted by Statistics Canada, Saint-Léon-de-Standon had a population of  living in  of its  total private dwellings, a change of  from its 2016 population of .
In the 2021 Census of Population conducted by Statistics Canada, the population of Saint-Léon-de-Standon consisted of individuals in some of its private dwellings, an increase from the 2016 population count.