This study examines whether corp8rate governance mechanisms influence the market valuation of Nigerian deposit money banks. Focusing on CEO duality and board diligence (board size, meeting frequency, and independence), the study employs a panel research design using secondary annual report data to estimate the relationship between governance structure and firm value, proxied by market price per share. The results indicate that CEO duality has a significant positive association with firm value, suggesting that unified leadership was not penalized by investors during the period studied. Board diligence proxies, especially board size and meeting frequency, also show significant positive effects, demonstrating that markets reward observable oversight intensity. Board independence, however, did not exhibit a strong valuation effect, implying that formal separation without enacted control is not priced. The overall model fit confirms that governance is not incidental but meaningfully predictive of value in the banking sector. The findings contribute to the governance–value discourse by showing that the market distinguishes between enacted and symbolic governance and that duality outcomes are context-contingent rather than theoretically fixed