In the
2021 Census of Population conducted by
Statistics Canada, Saint-Tharcisius had a population of living in of its total private dwellings, a change of from its 2016 population of . With a land area of , it had a population density of in 2021. Mother tongue (2021): • English as first language: 0% • French as first language: 100% • English and French as first language: 0% • Other as first language: 1.2% ==Government==