The effect of calcination temperature and MgO crystallite sizes on the structure and catalytic performance of TiO 2 supported nano-MgO catalyst for the transesterification of soybean oil has been studied. The catalyst has been prepared by deposition–precipitation method, characterised by XRD, TEM, XRF, BET and FTIR and tested in a batch autoclave at 225°C. The soybean oil conversion after 15min of the transesterification reaction increased when the calcination temperature was increased from 500 to 600°C and decreased with further increase in calcination temperature. Some glycerolysis activity was also detected on catalysts calcined at 600 and 700°C after 45min of reaction. The soybean oil conversion during the transesterification reaction increased with the decrease in MgO crystallite size for the first 30min.