In recent years, voluntary environmental management has gradually attracted the attention of entrepreneurs and researchers. As a typical form of environmental management, it clearly demonstrates the growth of corporate environmental awareness. Based on the perspective of organizational legitimacy, this study explored firms’ motivations to adopt voluntary environmental management with the data of 104 Chinese manufacturers. The results from fuzzy set qualitative comparative analysis (fsQCA) showed that both internal and external legitimacy could lead to the implementation of voluntary environmental management. However, the stimulating effect of internal legitimacy on voluntary environmental management was greater than external legitimacy. In addition, there was a certain complementarity between internal legitimacy and external legitimacy. This study provided theoretical guidance for cultivating corporate environmental awareness and promoting the popularization of voluntary environmental management.