The increase in diversity among employees has prompted organizations to begin to craft their human resource strategy towards better diversity management which in turn will lead to greater employee performance. This research seeks to investigate the effect of workforce diversity (age, gender and experience) on employee performance (employee engagement and employee satisfaction) in the five (5) Domestic Systemically Important Banks (DSIBs) in Nigeria. The study adopted survey research design as its methodology. Data was collected from 1881 employees in the 5 DSIBs from the six (6) geo-political zones in Nigeria using questionnaires. Regression analysis and Structural Equation Modelling (SEM) – Maximum Likelihood was used for data analysis. The results showed a significant positive relationship between workforce diversity (age, gender and experience) and employee performance. The findings of this study will give guidelines on the management of workforce diversity in the Banking and financial sector towards improved employee performance. This study examines the effect of workforce diversity on employee performance in DSIBs in Nigeria which is a gap that the study sought to fill.