A simple, accurate, rapid, and sensitive method using liquid chromatographic-quadrupole time of flight mass spectrometric method has been developed and validated for the simultaneous estimation of telmisartan (TS) and hydrochlorothiazide (HCTZ) in marketed tablet formulation utilizing olmesartan medoxomil (OSM) as internal standard. Sample preparation employed a simple solvent extraction technique. Chromatographic separation of analytes and internal standard, OSM, has been achieved on a Thermo Accucore TM C18 column (50 × 4.6 mm i.d, 2.6 µ) using gradient elution with 10 mM ammonium acetate solution and acetonitrile at a flow rate of 0.4-0.6 ml/minute. Mass spectrometric detection was achieved by combined electrospray ionisation as interface in negative polarity mode. Upon MRM ion scan, precursor and product ions were observed at m/z 513.20, 287.11 for TS, m/z 295.94, 204.97 for HCTZ, m/z 557.18, m/z 401.18 for Olmesartan medoxomil, respectively. The method was found to be linear in the range 0.20 to 4.01 ng per injection volume (5 µl) for TS and 0.06 to 1.25 ng per injection volume (5 µl) for HCTZ with precision values (as coefficient of variance) <2%. The assay recovery values of TS and HCTZ were found to be 98.9% and 99.6%, respectively.