This study examined the relationship between workplace diversity and organizational performance of deposit money banks in Delta State, Nigeria. The research focused on key diversity dimensions which are age and ethnic diversity and their influence on organizational performance. A cross sectional survey design was adopted and data were collected from staff across selected deposit money banks in Delta state, using structured questionnaires administered to staff of Polaris, Access, Eco, First and Zenith banks. The responses were analyzed using descriptive and inferential statistics, including correlation and regression analysis. The findings revealed that workplace diversity, when effectively managed, has a significant positive impact on organizational performance. However, challenges such as communication barriers, unconscious bias, and resistance to change were identified. The study concludes that diversity is not merely a compliance requirement but a strategic tool for organizational performance in the banking sector. It recommends that banks adopt inclusive recruitment policies, provide diversity training, promote leadership diversity, and establish measurable diversity performance indicators to maximize the benefits of a diverse workforce.