A simple and rapid liquid chromatography–tandem mass spectrometry method was firstly developed for simultaneous quantification of neomangiferin, mangiferin, regaloside A, regaloside I, timosaponin BII, anemarsaponin E and timosaponin AIII in rat plasma after oral administration of Baihe Zhimu decoction, which plays an important role for the treatment of depression. The plasma samples were pretreated by a one-step direct protein precipitation with methanol. Separation of the seven components and scutellarin (IS) from endogenous components with high selectivity and sensitivity (LLOQ, 0.1–1.0 ng/mL) was achieved within 10 min using Poroshell 120 EC-C18 column (150 mm × 3.0 mm, 2.7 μm). A gradient mobile phase consisting of acetonitrile and water (containing 5 mM ammonium acetate) was applied at a flow rate of 0.4 mL/min. Detection and measurement were performed on an AB Sciex QTRAP® 5500 mass spectrometer in multiple reactions monitoring mode. The intra- and inter-day precisions were all within 15% and the accuracies were in the range of −10.4% to 14.5%. The recovery ranged from 90.8 to 113.8%. The validated method was successfully applied to pharmacokinetic study of the seven components in normal and chronic unpredicted mild stress-induced depression model rats.