AbstractGiven the environmental challenges facing organizations, there is an increasing interest in how to stimulate the green behavior of employees. This study focuses on how leaders foster green advocacy, a specific category of green behavior that refers to influencing others to demonstrate green behavior by sharing environmental knowledge and discussing environmental issues. Our study, using a sample of 363 employees of a Belgian grocery retail company, provides valuable insights on the complex role of leaders in stimulating green advocacy. The results reveal that environmentally‐specific transformational leadership is positively related to employees' green advocacy. Our results further provide insights into the underlying mechanisms explaining this relationship, as we find that environmentally‐specific transformational leadership is indirectly related to employees' green advocacy through environmental CSR and organizational environmental support. Finally, leadership integrity is found to positively moderate the direct as well as the indirect relationship between environmentally‐specific transformational leadership and green advocacy.