Objectives: To determine the prevalence and sociodemographic correlates for mental illness among inmates at Lusaka Central Prison, Zambia.Design: Cross sectional study.Main outcome measure: Mental illness.Results: Of the 206 inmates in Lusaka, 63.1% had current mental illness. Among the factors considered in the study, only marital status was significantly associated with mental illness. Married participants were 40% (OR=0.60; 95% CI [0.36, 0.98]) less likely to have mental illness compared with participants who were who were separated/divorced.Conclusions: A high prevalence of mental health problems was observed among inmates at Lusaka Central prison. Marital status should be considered in designing interventions to reduce the high prevalence of mental illness among inmates in Lusaka, Zambia