Implementation researchers may benefit from organization theories, which offer a host of existing, highly relevant, and heretofore largely untapped explanations of the dynamic interactions between organizations and their environments. Organization theories, which have roots in management and sociology, can describe, explain, and predict the complex relationships between organizations and features of their external context. We propose that implementation researchers apply organization theories to advance rigorous and theoretically grounded studies of the interplay between external context and implementation. In this essay, to exemplify, we applied several organization theories to discuss the implementation of SafeCare, a child maltreatment prevention program that has been implemented in 23 US states, largely by state- and county-level child welfare agencies. Specifically, we used organizational theories to help explain 1) why public child welfare agencies increasingly contract with community-based organizations to administer evidence-based interventions (EBIs), 2) why SafeCare is often the EBI of choice, and 3) the role of interagency collaborative teams in addressing local community-based organizations’ needs and resource constraints, thereby facilitating SafeCare implementation.