This study focuses on the impact of a sustainability leadership development program (SLDP) designed to develop staff members as leaders who encourage sustainability practices within institutions of higher education (IHE). Using the framework of community of practice (CoP), we explored the program's contribution by interviewing 16 staff members who had attended the program. At the individual level, we found that the SLDP provided participants with opportunities to learn from and with other members of the CoP and to engage them in debate about the various meanings of "sustainability", increasing their environmental awareness and their environmental involvement within the IHE's community. At the institutional level, the SLDP disseminated the college's socio-environmental mission statement, increased its administration's commitment and involvement, served as a platform for addressing local socio-environmental problems and initiated an Education-for-Sustainability (EfS) activists' network. However, the participants indicated that the SLDP had limited impact on the environmentalism of other staff members and that the on-going mentoring and support from the college administration was insufficient. This study highlights the importance of such EfS professional programs to the development of both staff members and entire institutions as sustainability leaders. It also suggests ways to increase staff involvement in institutional EfS discourse.