In light of the gap in research and practice, with regard to achieving the sustainability goals of green building, while maximizing combination with building-information-modeling (BIM) as a social system—a gap that is expressed in the absence of integration of all stakeholders—a managerial measure is proposed to integrate them and promote sustainable green building. By using a framework for implementing BIM as a social system, and through network analysis, an index is developed to assess its integration into the green building—the Green BIM Index. This measure consists of comparing a social benchmark for optimal implementation with the actual implementation, in a given project. The index is intended to help score the BIM integration level in a green building. Comparing the BIM management measure results with social benefit assessments, and the effectiveness of BIM in nine case-studies enables to understand project outcomes in terms of schedules, budgets, and quality. The paper demonstrates the index applicability, pointing to possible significant economic improvements through the implementation of BIM social capabilities. BIM management benchmarking is helpful for the comparative evaluation of similar projects incorporating green building with BIM, indicating the level of integration to improve benefits.