This study examines how involvement in four undergraduate faculty communities of practice is associated with faculty perceiving they improved in individual practices related to STEM reform. It is informed by the communities of practice and faculty change literature and utilizes data gathered through a survey of community members (n = 2503). The findings reveal engagement experiences and aspects of community design associated with three outcomes--learning and improving practice, developing skills for leadership and change, and networking. These findings contribute to recommendations for designing future STEM reform initiatives.