This work investigated the effect of CEO duality and board size on the performance of quoted Nigerian brewery companies. Corporate governance has been brought to limelight as a result of the dilemma faced by organizations ranging from large scale misappropriation of funds, excessive executive remuneration and unequal treatment of shareholders to total corporate failure. The objectives of this research were to: Determine whether chief executive officer (CEO) duality has any effect on firm's financial performance and to examine how board size influences the firm's financial performance, as independent variables while the performance variable used was Profit after Tax (PAT) as dependent variable. Multiple Regression test was used to estimate the relationship between CEO duality and board size as components of corporate governance and firm financial performance. This study adopted a descriptive research design and data was analysed using a multiple linear regression model. The findings reveal that there is an insignificant relationship between CEO duality and firm performance. The study also revealed a significant relationship between board size and increased performance. The study recommends that there is need to have a sizeable board for an effective increase in performance and that Chief Executive Officer (CEO) and chairman should be separated so that the performance of the firms will be carried out effectively without much interference.