Principals' efforts to support the implementation of interventions involve coordination among multiple actors in their social networks. However, less is known about how distinct features of these social networks are associated with principals' perceptions of the social validity of interventions. In this paper, we used Neal and Neal (Implement Sci 14:16, 2019. 10.1186/s13012-019-0860-z) implementation capital framework to test hypotheses about the associations between two features of principals' social networks (i.e., bonding and bridging social capital) and three aspects of social validity (i.e., acceptability, understanding, and feasibility). Specifically, we tested these hypotheses in a statewide representative sample of 180 Michigan secondary school principals supporting the implementation of early warning signs (EWS), a systems-level intervention to prevent student dropout. Consistent with our hypotheses, we found that bonding social capital was positively associated with acceptability and bridging social capital was positively associated with understanding. But, contrary to our hypotheses, bonding and bridging social capital were not associated with feasibility. Drawing on these findings, we discuss future directions for research and practice implications to improve principals' perceptions of the social validity of mental health interventions.