In this article, we explain the mechanisms that allow social enterprises to balance their missions, and the risk of mission drift as organizations grow. We empirically explore Incubator-BUS (I-BUS), a student organization within a private Brazilian university, which sought to incubate cooperatives for vulnerable groups. Although initially successful in balancing its missions, I-BUS then failed. We show how scaling-up can complicate the balancing of different missions within the same organization. We propose that, to balance their missions, social enterprises—especially recently formed and democratically managed enterprises—need not only “spaces of negotiation,” as suggested in the literature, but also “herding spaces” that connect an organization to its institutional context. We indicate why herding spaces are critical, but then show how scaling-up can result in organizational “compartmentalization” that undermines them.