<p>Global markets are converging through technological innovation and environmental stewardship, creating opportunities for financial technology (Fintech) and green finance to advance sustainable performance jointly. This systematic review, following the PRISMA framework, examines the interaction between Fintech adoption, measured through indicators such as ATMs per 100,000 adults, internet usage, mobile subscriptions, and bank branch density, and green finance metrics, including adjusted net savings, renewable energy consumption, and CO₂ emissions. Across 120 eligible studies synthesized in this review, Fintech is found to promote financial inclusion, lower transaction costs, and enhance service accessibility, while green finance channels capital into “low-carbon” technologies, renewable energy, and climate-resilient infrastructure. The integrated evidence indicates that these mechanisms are mutually reinforcing: digital platforms enhance access to and monitoring of sustainable investments, and green finance increases demand for transparent and efficient Fintech systems. The findings highlight that the Fintech and green finance nexus most strongly supports social sustainability through inclusion, while environmental impacts remain context-dependent. Policy priorities include closing digital divides, harmonizing sustainability regulations, and leveraging blockchain and AI-driven ESG analytics for transparency and measurable impact.</p>