Although the literature on social innovation has focused primarily on social enterprises, social innovation has long occurred within mainstream corporations. Drawing upon recent scholarship on social movements and institutional complexity, we analyze how movements foster corporate social innovation (CSI). Our context is the adoption of green information systems (“green IS”), which are information systems employed to transform organizations and society into more sustainable entities. We trace the historical emergence of green IS as a corporate response to increasing demands for sustainability (...) reporting, a key social innovation that environmental activists helped to create. Drawing upon extensive survey data from more than 400 U.S. firms, we then examine how managers perceived environmental activism in relation to broader field pressures for change and how their perceptions of both were related to green IS adoption. The results reveal that activists were more effective at influencing adoption indirectly by transforming organizational fields than by directly influencing corporate managers. Combined with the historical analysis, these findings suggest that CSI emerged out of ongoing interactions between activists, corporate managers, and other influential actors within a broader social innovation system. Activists helped to create conditions for social innovation, but corporations took the lead in developing new practices. (shrink)