In this research, the effect of the addition of tungsten over NiMo and CoMo catalysts supported on alumina for biodiesel production via hydroprocessing was investigated. The experiment was operated at a temperature range of 300-400 ˚C, hydrogen pressure of 40 bar and reaction time from one to four hours using carbided NiMo and CoMo catalysts supported on alumina with and without addition of tungsten. Three types of fatty acid, including of oleic acid, stearic acid and palmitic acid were used as raw materials. From the experimental studies, it was found that addition of tungsten could promote activity and diesel selectivity for both NiMo and CoMo catalysts. Oligomerization products are observed at lower than 350˚C with a short reaction time (normally less than 2 hours) while cracking products are mostly observed at high temperature and/or longer reaction time. The highest diesel yield of 66.9% was achieved for the hydroprocessing of oleic acid using NiMo with the addition of tungsten at 350˚C, 40 bar and 2 hours. Liquid products contained hydrocarbons in a range of C15-C18 and water while gaseous products were carbon monoxide, carbon dioxide and methane.