Abstract The production of biodiesel from refined sunflower vegetable oil over basic CaO/ZSM‐5 catalysts was investigated. Several catalysts with various loadings of CaO on ZSM‐5 were prepared, calcined at 800 °C, and characterized by N 2 adsorption‐desorption, X‐ray diffraction, Fourier transform infrared spectroscopy, and CO 2 ‐temperature‐programmed desorption techniques. Calcined catalysts were tested in the transesterification reaction and reaction conditions were optimized by varying the catalyst‐to‐oil ratio and reaction time. The most active catalyst was the CaO/ZSM‐5 catalyst with a 35 wt % loading which gave the highest fatty acid methyl ester yield. The high catalytic activity was attributed to the active basic sites generated following CaO addition. Furthermore, the catalyst demonstrated stability against the leaching process.