Drawing on upper echelon theory, this study investigates the impact of CEOs’ (chief executive officers) demographic characteristics on corporate environmental performance (CEP) in small and medium-sized enterprises (SMEs). We hypothesized that CEO characteristics, including gender, age, basic educational level, professional educational level, political connection, and ethnicity, affect SMEs’ environmental performance. Using the cross-sectional data analysis of 810 Vietnamese SMEs, this study provides evidence that female CEOs and CEOs’ educational level (both basic and professional) are positively related to the probability of CEP. We also find that based on the role of institutional environment on CEP, political connections had a negative effect on CEP in the context of Vietnam. Another finding is that SMEs with chief executives from ethnic minority groups show a higher level of the probability of corporate environmental performance than companies operated by Kinh chief executives. Since CEP is an essential dimension of corporate social responsibility, a strategic decision for SMEs, it is crucial for the company to select appropriate CEOs based on their demographic characteristics.