Transesterification of crude Jatropha oil in presence of tungstophosphoric acid (TPA) supported on activated carbon (AC) using ultrasound-assisted process was investigated. The generated catalysts were characterized for physical and chemical properties to examine the effects of different TPA loadings (15%, 20%, 25% w/w). The catalysts were then used in the transesterification of Jatropha oil with high free fatty acid content. The catalyst with 20% TPA loading achieved the best methyl ester yield, achieving 87.33% in just 40 min. The quality of the feed stock was varied by increasing the water content and FFA content to test the tolerance of the catalysts towards these parameters separately. The catalyst showed good water tolerance to a limit of 1% w/w and proven to be insensitive to the increment of FFA in the feed stock. The catalyst was also investigated for possible reusability and TPA leaching under ultrasonic conditions. (C) 2013 Elsevier Ltd. All rights reserved.