In the present work, a precise, accurate and selective stability-indicating RP-HPLC method has been developed and validated according to International Conference on Harmonization guidelines Q2-(R1) for the simultaneous quantitative determination of Tolterodine tartrate and Tamsulosin hydrochloride in bulk and its capsule formulation. The chromatographic separation was achieved on Hypersil octadecyl silane C18 (250 x 4.6mm, 5 μm) column at room temperature and mobile phase comprised of methanol: 0.05 M phosphate buffer, pH 7.0 in the ratio of 90:10 V/V. The flow rate of mobile phase was set at 1.0mL/min and compounds were monitored at 255nm using photodiode array detector. Tamsulosin hydrochloride and Tolterodine tartrate retention time were found to be 4.15±0.2 min and 8.42±0.2 min, respectively. The drug substances and products were subjected to acid hydrolysis, alkali hydrolysis, oxidative hydrolysis, photolytic and thermal degradation. The percent degradation of drugs was calculated in all stressed conditions. The analytical method validation parameters such as linearity, accuracy, precision, detection limits, quantitation limits and robustness indicate that drug substances and products were efficiently separated in present of their degradants and successfully applied for the routine analysis of Tolterodine tartrate and Tamsulosin hydrochloride in bulk and its capsule formulation in the quality control laboratory.