This study evaluates the potential of local fish waste oil as a feedstock for biodiesel via supercritical methanol transesterification (SCMT). Hexane was used as a cosolvent and the transesterification reaction was carried out in a continuous reactor under supercritical conditions. The response surface methodology (RSM) method was applied to analyse the effect of four independent variables, including the weight ratio of methanol to fish-waste oil (W), the reaction temperature (T), the pressure (P) and the feed flow rate (F), on the yield of the biodiesel production in supercritical methanol. According to the calculated optimal operating condition for the RSM, the values of W (22.3 weight ratio of methanol to fish waste oil), T (270°C), P (112.7 bar) and F (2.0 mL min–1) were achieved. Under the optimum conditions, the highest yield was estimated to be 94.6% (g/g). The obtained yield was found to be close to the theoretical yield (95.2%). This value suggests that the proposed strategy has a promising potential in the production of biodiesel fuel.