Catalytic conversion of un-pretreated Jatropha oil with high-acid value (13.8 mg KOH/g) to biodiesel was studied in ionic liquids (ILs) with metal chlorides. Several commercial ILs were used to catalyze the esterification of oleic acid. It was found that 1-butyl-3-methylimidazolium tosylate ([BMIm][CH₃SO₃]; a Brønsted acidic IL) had the highest catalytic activity with 93% esterification rate for oleic acid at 140 °C but only 12% biodiesel yield at 120 °C. When FeCl₃ was added to [BMIm][CH₃SO₃], a maximum biodiesel yield of 99.7% was achieved at 120 °C. Because metal ions in ILs supplied Lewis acidic sites, and more of the sites could be provided by trivalent metallic ions than those of bivalent ones. It was also found that the catalytic activity with bivalent metallic ions increased with atomic radius. Mixture of [BMIm][CH₃SO₃] and FeCl₃ was easily separated from products for reuse to avoid producing pollutants.