Transesterification of palm oil and methanol with KOH as a catalyst in biodiesel synthesis was studied in a microtube reactor. The first part is the investigation on the influences of catalyst amount (5-13mg/g, 0.5-1.3 mass%), reaction temperature (52-70 degrees C), methanol-to-oil molar ratio (4.5:1-9:1), and residence time (5-20s) on fatty acid methyl ester content (%FAME). The optimal %FAME of 97.14% was achieved with the catalyst amount of 10mg/g (1 mass%), operating at 60 degrees C, and using a methanol-to-oil molar ratio of 6:1 and a residence time of 5s. High %FAME was obtained at low residence time due to the small size of droplets in the micro-channel reactor. The second part deals with the effect of mixer and reactor geometry. A comparison between %FAME obtained from the synthesis in a batch stirred-tank reactor and in a microtube suggested that the reaction proceeded much faster for the latter. The use of a T-mixer provided superior reaction performance compared to the J-mixer throughout the conditions studied.