Reverse phase high performance liquid chromatographic method has been focused with the aim of reducing analysis time and maintaining good efficiency. The present work describes a rapid, simple, precise, selective stability indicating RP-HPLC method for simultaneous estimation of Atazanavir and Cobicistat in tablet dosage forms. A Phenomenix C8 column of 250 × 4.6 mm internal diameter, 5 μm particle size with mobile phase consisting of O.1 M ammonium acetate and methanol of HPLC grade in the ratio of 1:1 was used. The flow rate was maintained at 1.2 ml/min. The effluents were monitored at 268 nm. The detector response was found to be linear over a concentration range of 30-90 mcg for atazanavir and 15-45 mcg for cobicistat. The retention times of atazanavir was found to be 3.576 min and Cobicistat 6.592 min. The correlation coefficients of atazanavir and cobicistat was 0.999 with equation y=43363x and y=59029x. Recovery of the method was 98-102%. According to ICH guidelines, the newly developed method has been validated in terms of accuracy, specificity, linearity, precision and robustness. Inorder to demonstrate the stability indicating power of the developed method forced degradation studies were performed for atazanavir and cobicistat by subjecting them to stress conditions including acidity, alkalinity, oxidation, photolysis and thermal degradation. The described method can be successfully employed for the quality control analysis of Atazanavir and Cobicistat in formulations.