Background: The benefits of religiosity in mental health has been documented in extant literature. However the relationship between religiosity and medical students’ attitude to mental illness has not been explored by previous studies. This study aimed to determine the relationship between religiosity and the attitude of medical students in a Nigerian university to mental illness. Methods: Fifth year medical students completed a sociodemographic and career choice questionnaire, Duke University religiosity index (DUREL) and Mental Illness: Clinician Attitude (MICA, medical student version) questionnaires. Results: Fifty four consenting medical students (male=36, female=18) completed the questionnaires. The frequency of religious service attendance (organized religious activity) had a significant negative correlation with the students’ attitude to mental illness (p= 0.021). Female medical students had significantly lower MICA scores, indicating a less stigmatizing attitude to mental illness compared to male students (p= 0.035). Conclusions: This study suggests that frequency of religious service attendance is an important variable to consider among factors influencing medical students’ attitude to mental illness. Findings from this study may be used by future interventions targeted at reducing stigma to mental illness among medical students.