Mediterranean migrant men living in France have lower mortality and morbidity than local-born populations for nutrition-related noncommunicable diseases (NR-NCD). We studied diet quality and its influence on NR-NCD in Tunisian migrants compared with 2 nonmigrant male groups: local-born French and nonmigrant Tunisians, using a retrospective cohort study. We performed quota sampling (n = 147) based on age and place of residence. Using logistic regression models, components of the Diet Quality Index-International (DQI-I) were tested as potential mediators for the effect of migration on overweight, hypertension, hypercholesterolemia, type-2 diabetes, and cardiovascular diseases (CVD). The total DQI-I score revealed good overall diet quality (∼60/100) for all groups. Migrants scored higher than the French in variety, adequacy, and moderation and lower than Tunisians in overall balance. Migrants displayed a lower prevalence of overweight than French, lower prevalence of diabetes and CVD than Tunisians, and lower prevalence of hypertension and hypercholesterolemia than the 2 nonmigrant groups. No mediator was found for overweight. Diet adequacy, fruits, and vitamin C were mediators of the difference in hypercholesterolemia between migrants and French and the effect on hypertension was mediated by diet adequacy and fiber. Compared with Tunisians, the effect of migration on hypercholesterolemia was mediated by saturated fat. No mediator was found for hypertension, diabetes, or CVD. Despite increasing NR-NCD levels in both France and Tunisia, migrants appear to have conserved some healthy dietary characteristics that partly explain their difference in NR-NCD with local-born French, but other lifestyle factors may contribute to the favorable effect of migration.