Abstract Background It remains unknown whether coronavirus disease 2019 (COVID-19) patients with bipolar disorders (BDs) are at an increased risk of mortality. We aimed to establish whether health outcomes and care differed between patients infected with COVID-19 with BD and patients without a diagnosis of severe mental illness. Methods We conducted a population-based cohort study of all patients with identified COVID-19 and respiratory symptoms who were hospitalized in France between February and June 2020. The outcomes were in-hospital mortality and intensive care unit (ICU) admission. We used propensity score matching to control for confounding factors. Results In total, 50 407 patients were included, of whom 480 were patients with BD. Patients with BD were 2 years older, more frequently women and had more comorbidities than controls without a diagnosis of severe mental illness. Patients with BD had an increased in-hospital mortality rate (26.6% v. 21.9%; p = 0.034) and similar ICU admission rate (27.9% v. 28.4%, p = 0.799), as confirmed by propensity analysis [odds ratio, 95% confidence interval (OR, 95% CI) for mortality: 1.30 (1.16–1.45), p < 0.0001]. Significant interactions between BD and age and between BD and social deprivation were found, highlighting that the most important inequalities in mortality were observed in the youngest [OR, 95% CI 2.28 (1.18–4.41), p = 0.0015] and most deprived patients with BD [OR, 95% CI 1.60 (1.33–1.92), p < 0.001]. Conclusions COVID-19 patients with BD were at an increased risk of mortality, which was exacerbated in the youngest and most deprived patients with BD. Patients with BD should thus be targeted as a high-risk population for severe forms of COVID-19, requiring enhanced preventive and disease management strategies.