This study examined post-consolidation impacts of corporate governance and debt structure on bank performance in Nigeria. It employed Generalised Methods of Moments (GMM) econometric technique on a panel sample of 12 Deposit Money Banks (DMBs) from 2005 through 2022. In congruence with the views of the agency theory and those of earlier scholars that smaller boards relate with higher levels of performance, our findings provide evidence in support thereof. Our results also support the positive roles of board composition and gender diversity inferring that the more independent and gender diverse a bank’s board, the better the performance. Our findings further argued that foreign diversity is not a value-relevant governance mechanism. The GMM estimates also found significant negative post-consolidation impact of debt-to-equity on ROE implying that the higher this debt variant, the worse the return on owners’ equity. Consequently, the results provide sufficient evidences that offer enough proof to support the Central Bank of Nigeria’s recommendations that DMBs maintain a minimum board size of seven, promote independent and gender inclusive boards, entrench gender quotas, promote policies that will attract foreign investors and encourage the banks to minimise their debt burden in order to maximise shareholders’ wealth, minimise weighted average cost of capital, the exorbitant cost of maintaining large boards as well as the conflicts associated with agency.