Christian Mennonites and Muslims worldwide have long established connections and worked together for peacebuilding and interfaith relationship building. Focusing on Indonesian Mennonites and Muslims, this chapter examines a relatively unexplored social phenomenon: the cooperation between these two religious communities in their attempts at fostering civic peace and social harmony through humanitarian work and interfaith relations in present-day Indonesia. The chapter aims to understand the factors, rationales, motives, as well as philosophical and practical considerations of their collaborations to shed light on the link between religion and peacebuilding.