Background: The health determinant model indicates that certain socio-cultural, socio-demographic, environmental, and lifestyle factors influence health status and wellbeing of any population group in any given nation Previous studies have suggested the need for regional and interregional comparison of health inequalities due to the interaction of these factors. Aims: This study investigated mental health indicators and cognitive health status by sex and ethnicity among university students in Nigeria. Method: The study was cross sectional. Full time university students were recruited from six universities within the major three ethnic groups in Nigeria. Data collection was with an anonymous questionnaire. One thousand five hundred and forty-nine responses were valid, while 563 responses were rejected for missing data especially sex and ethnicity. The variables examined were, psychosomatic health complaints and cognitive behaviours. Descriptive tests, chi-square tests and analysis of variance (ANOVA) tests were conducted. Results: With regard to mental health indicators, the results showed that while depression indicate significant differences by gender and ethnicity, life satisfaction showed significant differences by ethnicity alone. Cognitive health status showed sex*ethnicity interaction effect for self-efficacy, sense of coherence and powerful others locus of control. Conclusion: The findings indicated that the mental health of female students in the sample was poorer than those of male students; with female students from the Hausa ethnic group, demonstrating the worst possible health outcome.