Thiosultap-disodium (thiosultap) has been identified to be the potential alternative to monocrotophos and methamidophos for controlling bagworms and leaf earting caterpillars infestation in oil palm plantations. This article reports a simple and fast method of determining thiosultap residue in palm oil matrix using liquid chromatography coupled to a triple quadrupole mass spectrometer. The proposed method has been inhouse validated . Method recoveries were found to be satisfactory within the range of 72% to 103%, method precision was good with a relative standard deviation (RSD) of 4% to 6% for repeatability and RSD of less than 12% for intermediate precision. Method limit of detection and determination were estimated from matrix matched calibration curves, the values were 2.9 ng ml-1 and 8.7 ng ml-1, respectively. The fact that no maximum residue limit has been set for thiosultap in palm oil internationally, suggesting that the default value of 0.01 mg kg-1 maximum allowable limit is to be enforced. An analytical method that will enable the determination of thiosultap residue at this default level therefore is required to facilitate the monitoring of potential thiosultap residue contamination in palm oil traded in Malaysia.