This study explores how digital financial literacy shapes sustainable investment choices among postgraduate students. Surveying 109 students from Tamil Nadu, we found that while most use financial apps daily, only one in five has actually invested in sustainable options—despite many more expressing interest. The results were striking: students with stronger digital financial literacy and better fraud awareness were far more likely to make sustainability-conscious investment decisions, with these two factors explaining nearly 86% of sustainable investment behaviour. The platforms students used also mattered significantly, accounting for 81% of the variation in their sustainable financial choices. However, a clear gap emerged between awareness and action—students know about sustainable investing but aren’t translating that knowledge into behaviour. This suggests that beyond building digital skills and scam awareness, young adults need practical nudges—through college curricula or public campaigns—that help convert good intentions into real-world choices. In an increasingly digital financial landscape, such efforts aren’t just about smarter investing; they’re about cultivating thoughtful, resilient citizens.