A simple, rapid and accurate liquid chromatography-electrospray ionization-tandem mass spectrometry method was developed and validated for quantification of mangiferin in rat plasma. After the addition of the internal standard (IS) paracetamol, plasma samples were pretreated by protein precipitation. Chromatographic separation was carried out on a C(18) column by isocratic elution with methanol-acetonitrile-1% acetic acid (40:3:57, v/v/v). The detection was performed on a Sciex API 3000 LC/MS/MS with TurboIonSpray ionization (ESI) inlet in the positive ion MRM mode. Good linearity was achieved over the concentration range of 3.01-601 ng/mL. Intra- and inter-day precisions were less than 9.1%, and accuracy ranged from 100.5% to 104.0%. The pharmacokinetic profiles of free mangiferin at three dose levels and mangiferin in Zhimu decoction and Zhimu-Huangbai decoction were studied for the first time in rats by this method. After single intragastric administration of free mangiferin 17.5, 35 and 70 mg/kg, C(max) and AUC increased but non-proportional to the doses. At the same dose level (35 mg/kg), C(max) and AUC of mangiferin in two decoctions were significantly higher than the corresponding values of free mangiferin.