Dillenia indica L., commonly known as elephant apple, is traditionally used in northeast India to manage gastrointestinal disorders, especially during summer. In this study, the fruit collected from the northeast region was subjected to aqueous extraction, followed by phytochemical characterization using UV-Vis, FTIR, and GC-MS. Total alkaloidal content, total phenolic content, and total flavonoid content are also determined. The phytochemical quantitative analysis revealed the presence of alkaloids, phenolic, and flavonoid compounds. UV-Vis spectroscopy revealed prominent absorption peaks associated with polyphenolic and flavonoid compounds, while FTIR spectra confirmed the presence of functional groups characteristic of phenols, flavonoids, triterpenoids, glycosides, and carbohydrates. GC-MS profiling identified a total of 33 phytoconstituents, highlighting the extract’s rich chemical composition. Experimental results showed significant antibacterial effects against E. coli at 540 µg/ml; the extract inhibited 75.12% of planktonic growth and produced a 6.95 mm zone of inhibition when compared with gentamicin. Fluorescence microscopic observations further validated biofilm disruption and reduced bacterial motility and bacterial virulence through protease activity. Additional assays demonstrated reductions in bacterial motility, extracellular polymeric substance production, and protease activity mechanisms critical for bacterial virulence and biofilm stability. The presence of phenolics, flavonoids, and alkaloids might contribute to its synergistic biological activity. These findings support the traditional use of the fruit in managing gastrointestinal ailments and provide scientific validation of its antibacterial and anti-biofilm potential. The study offers a foundation for future biological research and possible therapeutic applications.