This study investigates the impacts of implementing a comprehensive Green Management Plan in the Bank Mellat Construction Company of Iran. The primary objective is to evaluate various dimensions of green management and its effects on the organization’s environmental, economic, and social indicators. The research adopts a mixed-methods approach combining qualitative and quantitative analyses. In the qualitative phase, insights were gathered through in-depth interviews with 12 experts in green management and construction. In the quantitative phase, data from 180 experienced employees of the organization were analyzed. The findings reveal that the implementation of the plan has led to significant and positive improvements in environmental indicators, including reduced energy consumption, increased use of renewable energy sources, improved waste management, and lower levels of environmental pollution. Furthermore, educational programs, individual incentives, and green-related events have contributed to raising employee awareness and fostering an environmental culture within the organization. Additionally, the commitment and support of senior management have played a key role in the successful implementation of the plan. This study emphasizes that green management is an effective tool for promoting sustainable development and enhancing the economic and environmental performance of organizations. Moreover, the Causal Loop Diagram (CLD) model developed in this research serves as an efficient tool for identifying the interactions among key variables and improving organizational planning. The findings can serve as a model for other industries aiming to advance sustainability and environmental management.