Background: Differences in neonatal mortality among immigrants have been documented in Belgium and elsewhere, and these disparities are poorly understood. Our objective was to compare perinatal mortality rates in immigrant mothers according to citizenship status. Methods: This was a population-based study using 2008 data from the Belgian birth register data pertaining to regions of Brussels and Wallonia. Odds ratio (OR) and 95% confidence intervals (95% CIs) for perinatal mortality according to naturalization status were calculated by logistic regression analyses adjusting for parents’ medical and social characteristics. Results: Four hundred and thirty-seven perinatal deaths were registered among 60 881 births (7.2‰). Perinatal mortality rate varied according to the origin of the mother and her naturalization status: among immigrants, non-naturalized immigrants had a higher incidence of perinatal mortality (10.3‰) than their naturalized counterparts (6.1‰) with an adjusted OR of 2.2, 95% CI (1.1–4.5). Conclusion: In a country with a high frequency of naturalization, and universal access to health care, naturalized immigrant mothers experience less perinatal mortality than their not naturalized counterparts.