Employee green behavior is one of the challenges facing organizations to enhance their environmental performance and achieve Environmental sustainability goals. Hence, the importance of identifying its determinants grows. Accordingly, the current study aimed to determine the moderating impact of green self-efficacy in the relationship between responsible leadership and employee green behavior in the Egyptian pharmaceutical sector firms. To achieve this goal, two main hypotheses were developed. Using survey, primary data were collected from Stratified sample of 320respondents in 15 firms of the Egyptian pharmaceutical sector. Using structural modeling partial squares SEM-PLS method, results confirmed that there is a significant positive relationship between responsible leadership and the employee green behavior, moreover green self-efficacy significantly moderated and enhanced this relationship. Finally, results have been discussed, theoretical and empirical implications were introduced, likewise its limitations and suggestions for future research.