In this study, simultaneous transesterification and esterification of high acid value sunflower oil to fatty acid methyl esters was studied using Amberlyst 46 as a heterogeneous catalyst. The influence of reaction conditions such as molar ratio of methanol/oil, reaction time, and reaction temperature was investigated. The highest fatty acids methyl esters yield of 75.8% was obtained in presence of 6 wt% oleic acid content under reaction conditions of 20 wt% Amberlyst 46 catalyst amount, 6/1 methanol/oil molar ratio, reaction temperature of 130 degrees C, and reaction time of 10 h.