In the 2021 Census of Population conducted by Statistics Canada, Saint-Nazaire-de-Dorchester had a population of  living in  of its  total private dwellings, a change of  from its 2016 population of .
The 2021 Census of Population by Statistics Canada recorded a population for Saint-Nazaire-de-Dorchester that lived in some of its total private dwellings, with an increase from the 2016 population figure.