HIV/AIDS is associated with significant mental health morbidity in high-income countries, and depression associated with HIV/AIDS has been linked with faster disease progression and reduced drug adherence. However, research on mental health is scarce in sub-Saharan Africa where infection levels are highest. This cross-sectional study of 220 HIV-positive outpatients at a dedicated Tanzanian HIV/AIDS care centre assessed sociodemographics, clinical variables and prevalence of ICD-10 common mental health diagnoses via a standardised psychiatric questionnaire (the Clinical Interview Schedule-Revised). Depression or mixed anxiety and depression was identified in 15.5% of subjects, with 4.5% suffering from other anxiety disorders. This suggests routine HIV care in sub-Saharan Africa should include assessment and treatment of mental health issues.