A magnetic core‐mesoporous shell KOH/Fe3O4@γ‐Al2O3 nanocatalyst was synthesized using the Fe3O4@γ‐Al2O3 core‐shell structure as support and KOH as active component. The prepared samples were characterized by X‐ray diffraction (XRD), field‐emission scanning electron microscopy (FE‐SEM), energy‐dispersive X‐ray spectroscopy (EDS), Fourier transform infrared (FTIR), Brunauer‐Emmett‐Teller (BET), and vibrating sample magnetometry (VSM) techniques. Transesterification of canola oil to methyl esters (biodiesel) in the presence of the magnetic core‐mesoporous shell KOH/Fe3O4@γ‐Al2O3 nanocatalyst was investigated. Response surface methodology (RSM) based on the Box‐Behnken design (BBD) was employed to optimize the influence of important operating variables on the yield of biodiesel. A biodiesel yield of 97.4 % was achieved under optimum reaction conditions. There was an excellent agreement between experimental and predicted results.