The purpose of this paper is to confirm the negative relationship between CEO hubris and firm performance as suggested in prior research, and to investigate how this relationship varies depending on managerial control conditions. CEO hubris can generate errors in the strategic decision-making process, which can consequently lead to poor firm performance. However, the strength of this relationship may vary depending on how executives are controlled. When managerial control is strong, the impact of CEO hubris on firm performance may be reduced, and conversely, when control is weak, its impact may be amplified. This is because when internal and external managerial monitoring and control mechanisms are in operation, the likelihood that CEO hubris translates into actual corporate decision-making is reduced. Accordingly, this study proposed the board of directors and chaebols as managerial control mechanisms in the Korean corporate environment and analyzed the effects of these control mechanisms on the relationship between CEO hubris and firm performance. The analysis results confirmed a negative relationship between CEO hubris and firm performance, and this negative relationship was attenuated when board independence was high or when the firm belonged to a chaebol. The findings of this study suggest that when control mechanisms over the CEO are well-established, the negative effects of the CEO's cognitive biases on the firm can be mitigated.