Abstract: The objectives of this research were to develop a biodiesel production process from palm oil using a downflow bubble column reactor and study the effects of reaction temperature, methanol-to-oil molar ratio and catalyst (NaOH) concentration. The conversion of triglycerides to methyl esters was determined by nuclear magnetic resonance spectroscopy. The optimum condition for transesterification of palm oil and methanol catalyzed by NaOH was found to be: methanol-to-oil ratio of 6:1, NaOH concentration of 0.5 wt.% and reaction temperature of 50 °C. At the optimum condition, the conversion of 95.7% was achieved. A mathematical model was developed based on three-steps first-order kinetics with a mass transfer factor to describe the experimental results. It was found that the developed mathematical model well described the production of biodiesel using a downflow bubble column reactor.