AbstractKurarinone, a natural prenylated flavonone isolated from Sophora flavescens, has been exhibited various activities. This study aimed to establish a simple and sensitive ultra‐high performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) method for determining kurarinone in dog plasma. Acetonitrile‐mediated precipitation was applied for sample pretreatment. Chromatographic separation was achieved on a Waters ACQUITY HSS T3 (100 × 2.1 mm, i. d., 1.8 μm) column with gradient elution using water containing 0.1% formic acid and acetonitrile as mobile phase. Quantitation was performed using an electrospray ionization source in negative multiple reaction monitoring mode. The linearity of this method was over the concentration range 0.1–500 ng/mL with the lowest limit of quantification (LLOQ) of 0.1 ng/mL. The intra‐ and inter‐day precision was less than 10.51% and the accuracy ranged from 94.85% to 97.72%, respectively. The extraction recovery of kurarinone in dog plasma was more than 82.37% and no significant matrix effect was observed. The analyte was stable under tested storage conditions. The validated method was further successfully applied to a preclinical pharmacokinetic study of kurarinone in dog after a single intravenous (2 mg/kg) and oral (20 mg/kg) administration. The results revealed that kurarinone was rapidly absorbed into plasma with good bioavailability (38.19%) and low clearance.