<p>This study provides novel empirical evidence on the role of green supply chain management (GSCM) in enhancing the sustainable performance (environmental, social, and economic outcomes) of restaurants in a developing country’s context. Focusing on Tanzania’s restaurant industry, an often overlooked sector in GSCM research, this quantitative study examines both the direct impact of GSCM on sustainable performance of restaurants, and the moderating influence of competitive pressure in such a relationship. Guided by the Natural Resource Based View Theory and Institutional Theory, a conceptual framework was tested using partial least squares structural equation modelling (PLS-SEM) and cross-sectional data collected from 386 restaurant managers and supervisors in Arusha between July and December 2024. The results show that GSCM significantly improve environmental, economic, and social performance, with the strongest effect observed on environmental outcomes. Furthermore, the study uniquely reveals that competitive pressure intensifies the positive effect of GSCM on environmental performance, while its moderating role on social and economic outcomes remains insignificant. By targeting the under researched interuction of GSCM, competition, and sustainability within the restaurant industry of a developing economy, this research fills a critical gap in the literature. The results provide practical guidance for policy makers, decision makers, and industrial professionals aiming at promoting sustainability through green supply chain management in the growing restaurant industry of developing countries.</p>