Global warming and pollution instigated by fossil fuel combustion have led environmental agencies to advocate for eco-friendly renewable fuels. Biodiesel is a green and renewable fuel produced by the transesterification reaction of vegetable oil/animal fat with short-chain alcohol in the presence of a catalyst. Biodiesel production has been affected by the cost of production mainly due to the cost of feedstock. This work presents biodiesel production using waste margarine oil and response surface methodology (RSM) for process optimisation. The transesterification of waste margarine oil was carried out using sodium hydroxide (NaOH) as a catalyst under atmospheric pressure in a lab-scale batch reactor. Central composite design (CCD) was used to optimise four parameters: methanol-to-oil ratio (3-15 mol/mol), catalyst ratio (0.3-1.5 wt.%), reaction time (30-90min), and reaction temperature (30-70^oC). Numeral optimisation was performed, and an optimum yield of 94.024% was obtained at a 9.6 mol ratio, 0.96 wt. % catalyst ratio, 63 min reaction time, 52 ^o C reaction temperature, and a low standard error yield of 0.576 %. Analysis of variance (ANOVA) showed that the methanol-to-oil ratio had the highest influence on the biodiesel yield, followed by the catalyst ratio, and reaction time had the least impact after temperature. The kinetics study describes that the reaction is controlled by pseudo-first order, and the activation energy was found to be 62.41 kJ/mol. It was concluded that biodiesel could be produced using waste margarine oil as a cost-effective feedstock optimised by RSM.