Objective Little attention has been given, so far, to the early colonial diet in New France from an isotopic perspective. Historical records that compare France to New France suggest a shift toward a more diverse diet, including a higher protein intake due to an improvement in living conditions in the New World, despite the retention of ancestral dietary habits. This hypothesis will be explored here. Materials and methods Stable carbon (organic and mineral) and nitrogen isotopes were measured on 43 individuals from Notre Dame cemetery (first Catholic parish church cemetery in Montreal, 1683–1803) as well as 13 French compatriots from La Rochelle, France (Protestant Hospital Cemetery, 1765–1792). Intragroup variation (age at death, sex, and/or burial location) was investigated and compared to compiled data from various northeastern North American sites (N = 99). Results The Notre Dame sample means are as follows: −19.6‰ versus VPDB for δ13Ccollagen, −12.22‰ versus VPDB for δ13Ccarbonate, and 11.5‰ versus AIR for δ15N. They are significantly lower than both La Rochelle (−18.4‰, −11.67‰, and 12.7‰, respectively, p ≤ .005) and the northeastern North American groups used for this comparison (p = .000). Discussion The isotopic values obtained from Notre Dame cemetery suggest that the diet was mainly based on C3 resources with limited C4 resources. Although different from all comparable contemporary sites, colonial Montreal's diet remains most similar to La Rochelle, France. This study agrees with historians who have suggested that French dietary traditions seem to have been retained among the early colonial inhabitants of Montreal.