Transesterification of palm oil with methanol using a potassium hydroxide (KOH) catalyst to form fatty acid methyl ester (FAME) commercially known as biodiesel was performed in a millichannel reactor. In this study, a transparent Teflon tubular reactor with the inner diameter of 1.59 mm at 60 °C was carried out to produce FAME. Residence time was changed by changing the tube length and flow rate. The residence time of 69 s is required to achieve more than 88 of ester content. The relationship between ester content and flow pattern was also investigated. © (2014) Trans Tech Publications, Switzerland.