While corporate sustainability is attaining more spotlight, the role environmental nongovernmental organizations (ENGOs) play in corporate sustainability programs (CSPs) continues to be ambivalent. Some ENGOs take on policing roles towards CSPs, whereas others form "Green Alliances" with corporations to enhance their CSPs. This paper takes a deep dive into CSPs, ENGOs, and communication problems associated with CSPs, namely, reporting inadequacies and greenwashing. Potential angles from which ENGOs can help foster or enhance corporate sustainability are then identified and examined. This empirical study examines several factors to improve corporate sustainability through partnerships with ENGOs. From the survey results, the top areas in which ENGOs can influence CSPs are determined-these include external value creation and the identification and monitoring of corporate negative environmental impact.There is evidence found in support of a correlation between trust in ENGOs and the perceived effectiveness of Green Alliances.