Background: The prevalence of psychiatric illness in correctional settings is significantly elevated, with higher than community rates reported in most mental disorders. The prison is a correctional institution in which inmates have limited liberty, autonomy, and communication with family and friends. This can be devastating to some inmates thereby leading to deterioration in their physical, psychological and social wellbeing. The study was aimed to determine the prevalence of axis 1 psychiatric disorders and associated factors among prison inmates in Jos, Nigeria. Method: This was a cross-sectional descriptive study carried out in Jos maximum security prison among 608 inmates. Two sets of data collection instruments were used namely (General Health Questionnaire) GHQ-28 and (Composite International Diagnostic Interview) CIDI. SPSS statistical software package for windows version 15.0 was used for data analysis and test of significance was set at P < 0.05. Results: Prevalence of psychiatric disorders was 347 (57%), substance use disorder was the commonest disorder found in 169 (48.7%). Psychiatric morbidity was significantly associated with age (p = 0.034) and prison status (p = 0.01). Conclusion: This study showed that there was a high rate of psychiatric disorders among prison inmates in Nigeria, which should be a concern to health care policy makers in the country. Recommendation: The establishment of functional psychiatric services with adequate manpower in prison will assist in the detection, treatment and correction of inmates.