Environmental sustainability has become an increasingly important strategic concern for manufacturing firms operating under resource constraints and regulatory pressure. In this context, Green Supply Chain Management (GSCM) offers an integrated approach for aligning environmental responsibility with operational objectives. This study investigates the extent to which GSCM practices influence environmental and operational performance in selected manufacturing industries of Shivamogga District, Karnataka. Primary data were collected from 120 manufacturing firms representing agro-based, engineering, food processing, and small-scale industrial sectors. The analysis employs advanced inferential statistical techniques, including Exploratory and Confirmatory Factor Analysis, Structural Equation Modeling, hierarchical regression, and bootstrapped mediation analysis using SPSS and AMOS. The results indicate that green procurement and reverse logistics significantly strengthen environmental performance, while green manufacturing practices exert a direct and substantial effect on operational efficiency. The findings provide empirical evidence that GSCM functions not merely as a compliance mechanism but as a strategic performance enabler for manufacturing firms in semi-urban industrial regions. The study contributes to the growing body of sustainability literature by offering district-level insights and practical implications for managers and policymakers seeking to promote sustainable manufacturing practices.