Background: The combination therapy of Vildagliptin and Nateglinide was found to be an effective and safe in type 2 diabetes mellitus.Objectives:Study a new, simple, precise, accurate and specific stability indicating RP-HPLC and First-order derivative UV spectrophotometric method for the simultaneous estimation of Vildagliptin and Nateglinide in combination. Materials and Methods:The chromatographic separation was achieved isocratically. The mobile phase, Acetonitrile: Phosphate buffer (70:30; % v/v; pH 3.2) was selected as it was found to resolve the peaks with better intensity. For UV spectrophotometric method, methanol was used as a solvent, the spectrum was recorded between 200-400 nm wavelengths, and all the zero-order spectrum (D0) were converted to first-order derivative spectrum (D1) using delta lambda 2.0 and scaling factor 4. 253 nm (zero crossing point of Nateglinide) and 270 nm (zero crossing point of Vildagliptin) were used for determination of Vildagliptin and Nateglinide respectively. The methods were proved linearin the concentration range of 5-25 μg/ml for Vildagliptin and9-45 μg/ml for Nateglinide. Both drugs were subjected to stress conditions including acidic, alkaline, oxidation, photolysis and thermal degradation. Results: The proposed methods were validated in terms of Linearity, Range, Accuracy, Precision, LOD, LOQ, Specificity, Robustness, System suitability tests and stability studies and itsresults were proved within limits. The results showed that Vildagliptin and Nateglinide were more sensitive towards thermal and acidic degradation, respectively. Conclusion:Both methods were highly sensitive, precise, accurate and applicable for the reliable quantitation in their combination