This study examines how green supply chain management supports sustainable organizational performance in Bangladesh’s ready-made garment sector. The study focuses on green garment organizations and investigates environmental, financial, and social performance dimensions. It develops a conceptual model linking green supply chain management, circular economy, managers’ green concern, and sustainable performance. The research applies a quantitative survey design and uses PLS-SEM for hypothesis testing. A total of 560 valid questionnaires were analyzed from managers and employees in green garment firms. The findings show that green supply chain management has a significant positive effect on sustainable organizational performance. Green supply chain management also positively influences circular economy practices. Circular economy has a significant positive effect on sustainable organizational performance and partially mediates the GSCM-SOP relationship. Managers’ green concern has a significant negative moderating effect, suggesting that additional green concern may weaken the GSCM-performance link in already green-oriented firms. Overall, the thesis contributes to sustainability, circular economy, and supply chain literature in the context of an emerging economy.