Polyphenolic substances obtained from the leaves of Vitex negundo have gained attention for its therapeutic benefits. To obtain the maximized antioxidant-rich polyphenolic substances from the Vitex negundo leaves via microwave-assisted extraction (MAE), Box–Behnken design (BBD) was employed to evaluate the influence of several variables of MAE on the total phenolic content (TPC) and total flavonoid content (TFC) as determined by Folin–Ciocalteu assay method and Aluminum Chloride assay method, and the antioxidant capacity as measured by DPPH and ABTS assay methods, respectively. Response surface methodology (RSM) was used for finding optimal extraction conditions. GC-MS analysis was conducted on the extract. The tocopherol content and anticancer potential were estimated using HPLC and MTT assay respectively. The ideal extraction parameters were found to be 14 min, 48 °C, 65 % (v/v) methanol concentration, and 14 ml of extraction solvent. The optimum experimental conditions produced the TPC and TFC values of 1.46 mg GAE/g of dried extract and 1.06 mg QE/g of dried extract respectively. Furthermore, the DPPH and ABTS assays results showed the optimum values of 53 % and 77 % respectively. 12 bioactive compounds were identified using GC-MS. The amount of tocopherol was found to be 414.87 µg/g. Lastly, the obtained leaf extract demonstrated its anticancer potential on PC3 cell lines. The findings demonstrated leaf extract’s potential as a useful source of polyphenols with strong antioxidant qualities that can be used in a variety of pharmaceutical applications.