In this study we investigate collaborative social innovation from a nonprofit sector perspective. More specifically, we explore how religious organizations, and their volunteers collaborate across organizational boundaries for social innovation, involving religious, public and for-profit organizations. For the emergence of multi-actor collaborations for social innovation, we find that interorganizational shared spaces facilitate the emergence ‐ strategic and serendipitous ‐ of shared ambitions, ideas and initiatives. Substantial impacts of such collaborations were found, in terms of learning, synergy, and commitment. Moreover, such processes led to renewed and expanded voluntary work.