Corporate Social Responsibility (CSR) has evolved from a discretionary philanthropic activity into a statutorily mandated and strategically embedded function of Indian commercial banks, particularly since the notification of Section 135 of the Companies Act, 2013. As financial intermediaries that mobilise savings and allocate credit across the economy, banks occupy a unique position from which their CSR choices can influence social, economic, and environmental outcomes at a scale disproportionate to their own balance sheets. This paper examines the CSR practices of Indian commercial banks and evaluates their contribution to the three pillars of sustainable development, namely economic viability, social equity, and environmental stewardship. The study maps the thematic priorities of bank-led CSR spending, contrasts the practices of public sector and private sector banks, and situates these practices against the Sustainable Development Goals (SDGs) framework. The analysis suggests that Indian banks concentrate CSR expenditure heavily on education, rural development, health, and financial inclusion, while environmental and green-finance initiatives, though growing, remain comparatively underdeveloped and unevenly disclosed. Public sector banks tend to treat CSR as a compliance obligation embedded in mandated spending, whereas several private sector banks increasingly integrate CSR with core business strategy, brand equity, and environmental, social, and governance (ESG) reporting. The paper identifies a persistent research gap concerning the long-term, outcome-level impact of bank CSR on sustainable development indicators, as most existing studies stop at describing expenditure patterns rather than measuring developmental change. The study concludes that a stronger regulatory push toward standardised impact disclosure, deeper integration of CSR with green banking, and a shift from output-based to outcome-based CSR evaluation are necessary if Indian commercial banks are to meaningfully advance the sustainable development agenda.