Objective: To assess the prevalence of common mental disorders (CMD) and the association of CMD with sociodemographic characteristics in the Brazilian Longitudinal Study of Adult Health (ELSABrasil) cohort. Methods: We analyzed data from the cross-sectional baseline assessment of the ELSA-Brasil, a cohort study of 15,105 civil servants from six Brazilian cities. The Clinical Interview Schedule-Revised (CIS-R) was used to investigate the presence of CMD, with a score X 12 indicating a current CMD (last week). Specific diagnostic algorithms for each disorder were based on the ICD-10 diagnostic criteria. Prevalence ratios (PR) of the association between CMD and sociodemographic characteristics were estimated by Poisson regression. Results: CMD (CIS-R score X 12) was found in 26.8% (95% confidence intervals [95%CI] 26.1-27.5). The highest burden occurred among women (PR 1.9; 95%CI 1.8-2.0), the youngest (PR 1.7; 95%CI 1.5-1.9), non-white individuals, and those without a university degree. The most frequent diagnostic category was anxiety disorders (16.2%), followed by depressive episodes (4.2%). Conclusion: The burden of CMD was high, particularly among the more socially vulnerable groups. These findings highlight the need to strengthen public policies aimed to address health inequities related to mental disorders