<p>The internationalization rhythm, which captures the irregularity of a firm’s foreign expansion and affects its performance significantly, serves as a key parameter of international management (IM). However, few studies have been found to investigate its antecedents, especially the roles of CEOs. Based on the upper-echelon perspective and two different samples of multinational enterprises (MNEs), this study found that narcissism and overconfidence, two most common personality traits of CEOs, exert different effects on their firms’ internationalization regularity. Moreover, board independence, the internal monitoring device, helps attenuate the effects of CEO narcissism and overconfidence. In contrast, media evaluation, the external monitoring device, does not significantly affect the effects of those two personality traits. Overall, the study contributes to the research of IM through delineation of the significant impacts of CEOs’ personality traits on their firms’ internationalization rhythm. It also distinguishes narcissism from overconfidence as well as internal monitoring mechanism from external one while highlighting the need to integrate corporate governance with IM studies. The implications of this study suggest that stakeholders should establish an independent and effective board to constrain the impacts caused by the personality traits of CEOs on firms’ internationalization regularity as they can significantly affect their firms’ performance.</p>