This study examines the effects of diversity of board members on financial performance of firms in the Nigeria. The quantitative and correlational research design was adopted. Using the purposive sampling method, 60 companies were selected from a population of 162 companies listed on boards of the Nigerian Exchange Limited and data were collected for periods from 2001 to 2020. The Panel Auto-Regressive Distributive Lag (ARDL) model was employed for the analysis. The findings report that board age portrayed positive relationship and was statistically significant across all financial performance indicators. Gender diversity exhibited positive relationships with net profit margin, return on assets and tobin q but portrayed negative relationship with market price. Ethnic diversity indicated positive relationships with net profit margin and market price, but negative relationships with return on assets and tobin q. The study concluded that board diversity has strong long run relationship with firms’ performance in Nigeria. More so, given existing financial performance measures, older directors tend to add greater value to firms than younger directors. Also, firms that have higher ratio of ethnic diversity in board of directors will usually outperform, financially, firms with lower ratio.