This research work studied the relationship between board characteristics,ownership structure and the firm value of listedpetroleum firms in Nigeria. From a population of fifteen firms, the study used six listed petroleum firms that had consistently published their annual audited financial reports from 2008 to 2015.The data was analyzed using the robust pooled-OLS multiple regression technique in view of the absence of panel effect in the data as confirmed by the result of Breusch Pagan Lagrangian Multiplier test. The results of the robust pooled-OLS regression analysis revealed that board independence, board size as well as managerial shareholding had a negative but significant relationship with firm value. In the case of board gender diversity, it was discovered that the inclusion of females on the board of petroleum firms in Nigeria had a positive and significant relationship with firm value.While ownership concentration has an insignificant relationship on firm value. In view of the findings, the study recommended an optimal board size of nine directors, beyond which an additional board member will create added costs greater than the benefit derivable from the added board member. Also, not less than two femalesare recommended on the boards of listed petroleum firms in Nigeria to improve firm value. In addition, concentrated shareholding should be encouraged at the level of 19%, but should not be above 74% of the firm‟s shareholding, while a large managerial ownership structure should be moderated to about 37% to reduce the abuse of shareholders resources.