A simple, sensitive and reliable method is described for simultaneous quantification of Carvedilol and its metabolite 4-Hydroxyphenyl Carvedilol in human plasma by using High-throughput liquid Chromatography–tandem mass spectrometric method. The method was carried out by on-line coupling of extraction with Cyclone P (50 mm × 0.5 mm 50 μm) HTLC(High-throughput liquid Chromatography) column by injecting 10μL plasma sample and chromatographic separation was performed with ACE C18 (50X4.6 mm, 5μm), followed by quantification with mass detector in multi reaction monitoring using ESI as an interface. The method was linear over a concentration range 0.1 to 250 ng/mL with a limit of Quantification of 0.1 ng/mL for both Carvedilol and 4-Hydroxyphenyl Carvedilol. Intra– and inter-day precision were less than 15%, respectively, and the accuracy was in the range of 91.6-106.2%. Stability assessment was also included. The total run time of analysis was 2.5 min. The validated method was successfully applied to bioavailablility and Bioequivalence study.