Deposit Money Banks (DMBs) play a vital role in a country's financial stability and economic growth by facilitating fund flows and offering crucial financial services. Despite efforts to improve employee efficiency within DMBs, the desired outcomes may not have been achieved due to a lack of emphasis on deep-level diversity. Understanding deep-level diversity is crucial for comprehending individual employees' complexities and their impact on performance. Unfortunately, many organizations, including DMBs, tend to prioritize surface-level characteristics, overlooking the nuanced qualities that define employees. This oversight contributes to challenges in optimizing employee performance, resulting in reduced efficiency within certain DMBs. Acknowledging and addressing deep-level diversity is imperative for organizations aiming to succeed in today's intricate global business environment. Hence, this study examined deep-level workforce diversity and employee efficiency in selected deposit money banks in Lagos State, Nigeria. The research employed a survey methodology, targeting a population of 4,871 employees from five chosen deposit money banks in Lagos State, Nigeria. A sample size of 464 was determined based on a sample size table provided by the research advisor. Data collection utilized a validated questionnaire with structured format. The reliability of constructs, measured through Cronbach's alpha coefficients, ranged from 0.70 to 0.94. A response rate of 78.9% was achieved. Data analysis encompassed descriptive techniques along with inferential statistics such as multiple linear regression. The findings revealed that deep-level workforce diversity had significant effect on employee efficiency in selected deposit money banks in Lagos, Nigeria (Adj. R 2 = 0.333; F (4,361) = 46.558, p < 0.05). The study concluded that deep-level workforce diversity enhanced employee efficiency in selected deposit money banks in Lagos, Nigeria. The study therefore recommended that management of deposit money banks should implement strategies to embrace and leverage deep-level workforce diversity to enhance employee efficiency and overall organizational performance.