<p>This study examines the relationship between sustainable finance and environmental sustainability as well as the moderating role of FinTech in BRICS countries. An advanced panel data procedure, including Driscoll–Kraay standard errors, feasible generalized least squares, dynamic fixed effects, and method of moments quantile regression, is applied to data from 2004 to 2023. The findings reveal that sustainable finance promotes green investment initiatives and enhances sustainability. FinTech complements these efforts by offering eco-friendly financial services and strengthening the nexus between sustainable finance and environmental sustainability. However, the results also indicate that the environmental impact of FinTech is not uniformly beneficial and may vary across countries, depending on structural and regulatory conditions. Overall, sustainable finance and FinTech have emerged as potential solutions to environmental challenges in BRICS countries. The study highlights the need for BRICS governments to strengthen integrated green FinTech regulation, enforce binding ESG-based green taxonomies, and align digital finance expansion with carbon pricing and sustainable investment standards to ensure that financial innovation translates into measurable environmental improvement.</p>