Biofuels have emerged as a prominent and environmentally-friendly alternative to traditional fossil fuels. Biodiesel, in particular, is recognized as a top contender for replacing petro-diesel, associated with pollution and environmental concerns. In the present research work, Acacia nilotica seeds were used as an indigenous non-edible feedstock for biodiesel production. The objective of current study was to employ the solvent-assisted direct transesterification approach for biodiesel production based on the simultaneous oil extraction and transesterification in one step. Ethyl acetate was used as a co-solvent, and due to the high free fatty acid content in Acacia Nilotica seed oil, the concentrated H2SO4 was used as a catalyst. The purpose of co-solvent is to improve the miscibility of Acacia oil into methanol which leading to attain maximum yield (98%) in shorter time (300 min) therefore this could be a promising approach for biodiesel synthesis economical and viable. To achieve maximum product yield, the study utilized a computational statistical optimization method rooted in the Box-Behnken response surface methodology (RSM) design. This method optimised key process parameters, including reaction time, temperature, molar ratio (methanol to oil), and catalyst quantity. The results of RSM (optimization of reaction parameters) shows that, 300min reaction time, a temperature of 55°C, a molar ratio of 21:1, and a catalyst quantity of 6% by weight of H2SO4, these were identified as the optimized process parameters that achieved a biodiesel yield of 98%. FT-IR and Gas chromatography (GC-FID) analyses indicated that the predominant fatty acids in Acacia nilotica oil were Linoleic acid (31%) and oleic acid (30%). Our investigation unveiled the effective utilization of cosolvent, enabling mild conditions for acid-catalyzed direct transesterification. This approach leads to the production of high-quality biodiesel from acid oil.