A simple, specific, accurate, precise and selective stability-indicating reverse phase high performance liquid chromatography method was developed for estimation of Umifenovir in bulk and formulation by analytical quality-by-design paradigm. Cosmosil C-18 column (250 x 4.6 mm x 5µ) at ambient temperature and UV detector at 258 nm wavelength was employed. The mobile phase was methanol:water (65:35 % v/v) adjusted to pH 3.0 and flowrate 0.8 ml/min. The method involved varying three key parameters (composition of mobile phase, flow rate and pH) and evaluating their effects on the responses. Box-Behnken design was employed for method development and optimized using statistical software. ICH guidelines were followed for method validation as well as forced degradation study. The stability of drug in stress conditions of acid/base hydrolysis, oxidation, thermal and photolytic degradation was evaluated