In this paper the authors proposed a simple, sensitive and selective liquid chromatography–tandem mass spectrometry (LC–MS/MS) assay method for the determination of mosapride in human plasma. This method employed mosapride–d5 as an internal standard (IS). Analyte and the IS were extracted form 100 µL of human plasma using solid–phase extraction with no drying, evaporation and reconstitution steps. The chromatographic separation was achieved on a C18 column by using a mixture of methanol and 5mM ammonium acetate (80:20, v/v) as the mobile phase at a flow rate of 1.0 mL/min. The linearity of the method was established in the concentration range 0.18–60.0 ng/mL with r2 ³ 0.99. The intra–day and inter–day precision (%CV) and accuracy results in five validation batches across five concentration levels were well within the acceptance limits. The validated method was found to be applicable to clinical studies.