<p>Soybean (<i>Glycine max</i>), a protein- and oil-rich crop, supplies approximately 80% of oil requirements globally. The crop is susceptible to a wide variety of phytopathogens, among them <i>Colletotrichum truncatum</i> (CT) causes pre- and post-emergence damping-off in seeds and seedlings, leading to significant yield loss in the soybean crop. Here in this study, we assess the antifungal efficacy of peppermint oil nanoemulsion (PNE) against <i>C. truncatum</i> and also evaluate the disease suppression potential of PNE on soybean crop through seed priming. During the evaluation of fungicidal potential, 1% treatment of PNE reduces the growth of <i>C. truncatum</i> by 80% under in vitro conditions. PNE treatments induce oxidative stress by ROS accumulation, as suggested by Nitro Blue Tetrazolium (NBT) staining. Consequently, this redox imbalance affects the defence mechanism, cytosolic leakage and disruption of essential cellular processes leading to cell death. During PNE stress, stress enzyme activities were suppressed, including superoxide dismutase (SOD) by 26% and glutathione peroxidase (GPX) by 63%, while oxidative stress leads to enhanced lipid peroxidation by (LPX) 22% and polyphenol oxidase (PPO), 28%. Notably, scanning electron microscopy revealed significant aberration in hyphal structure, confirming the antifungal efficacy of PNE. Moreover, GC–MS analysis of ethyl acetate extracts from treated fungal cells identified 28 compounds, including thymol, menthol, phenyl alcohol, p-menthane, phenol, 1-docosanol, and 1-octadecene, present at elevated levels, related to antifungal activity. In addition, the nurturing effect of PNE was evaluated by a seed germination assay; PNE-treated seeds showed improved seed germination compared to Pathogen alone-infected samples. These findings suggest a potential role of PNE as an eco-friendly alternative for managing <i>C. truncatum</i> in soybean cultivation.</p> Graphical Abstract <p></p>