A simple, specific, accurate, precise and reproducible method has been developed and validated for the simultaneous estimation of hydrochlorothiazide and Olmesartan medoxomil in combined dosage form by UV spectrophotometric method. UV spectrophotometric method includes Simultaneous equation method (Method I) 271.5 nm and 257.0 nm λmax of both the drugs were selected, absorbance Ratio method (Method II) 261.5 nm an isoabsorptive wavelength and 257.0 nm were selected for estimation of hydrochlorothiazide and Olmesartan medoxomil respectively and Three-wavelength method (Method III), two wavelengths were selected such that hydrochlorothiazide give same absorbances (263.8 and 278.4 nm) at two selected wavelength while third wavelength (316.5 nm) was such that olmesartan gives nearly zero absorbance. The two drugs follow Beer’s law over the concentration range of 5-25 μg/mL. The % recoveries of the both the drugs were found to be nearly 100 % representing the accuracy of the proposed methods. Validation of the proposed methods was carried out for its accuracy, precision, specificity and ruggedness according to ICH guidelines. The proposed methods can be successfully applied in routine work for the determination of hydrochlorothiazide and olmesartan medoximil in combined dosage form.