This study examines the impact of four main dimensions of Green Supply Chain Management (GSCM) i.e., Internal Environmental Management (IEM), Green Purchasing (GP), Eco-design (ED), and Collaboration with Suppliers and Customers (CSC) on firms' Sustainable Performance (SP) - (environmental, social, and economic). The study collected data through an adopted structured questionnaire from 190 respondents of the manufacturing firms located in the Khyber Pakhtunkhwa (KP) province of Pakistan. By employing Structural Equation Modelling (SEM) through SmartPLS, it is revealed that IEM, GP, and ED have a significant positive while CSC has an insignificant positive impact on firms' SP. By dividing the sample into China-Pakistan Economic Corridor (CPEC) aware and unaware groups, it is confirmed that IEM, GP, and ED have a significant positive while CSC has an insignificant association with firms' SP in the former group only as none of the other GSCM dimensions, except the significant positive coefficient of GP, has any significant relationship with firms' SP in the latter group. Besides enriching the literature, especially by exploring the role of CPEC awareness, the study also contributes to the theory by testing the assumptions of the rarely examined stakeholder salience theory in the nexus of GSCM-SP. The study also contributes to the practice by updating all the key stakeholders including the local industry, government, and CPEC authority that GSCM (IEM, GP, and ED) is a comprehensive and effective strategy for boosting firms’ SP and CPEC influencing their association positively.