AbstractPatients with bipolar disorder have higher rates of type 2 diabetes (T2D) compared to the general population. Neighbourhood deprivation is associated with T2D and bipolar disorder. The aim of this study was to explore the potential effect of neighbourhood deprivation on incident T2D in patients with bipolar disorder. This nationwide open cohort study (1997–2018) included adults in Sweden ≥20 years with bipolar disorder (90,780 patients) to examine the subsequent risk of T2D. The association between neighbourhood deprivation and T2D was explored using Cox regression analysis, with hazard ratios (HRs) and 95% confidence intervals (95% CIs). All models were conducted in both men and women and adjusted for individual‐level sociodemographic factors and comorbidities. Neighbourhood deprivation was significantly associated with T2D in patients with bipolar disorder. The HRs were 1.61 (95% CI 1.40–1.86) for men and 1.83 (1.60–2.10) for women living in high deprivation neighbourhoods compared to those from low deprivation neighbourhoods. After adjustment, these results remained significant: 1.35 (1.17–1.56) in men and 1.39 (1.20–1.60) in women living in high deprivation neighbourhoods. The suggested graded association of higher incident T2D among patients with bipolar disorder, observed when levels of neighbourhood deprivation increased, raises important clinical and public health concerns. The results may help develop a contextual approach to prevention of T2D in patients with bipolar disorder that includes the neighbourhood environment.