An efficient and sensitive RPHPLC method was developed and validated for the estimation of Sitagliptin Phosphate process impurities in drug substances which were identified and characterized by LCMS, FTIR, 1H NMR, C NMR techniques. The method was carried out on a Symmetry shield RP 18 column at 25°C using a 1 % Perchloric acid and acetonitrile in gradient mode of pump. The flow rate is 1.2 ml/min and detection was done at 210nm.The developed RP HPLC method was validated by testing specificity, precision, Forced degradation, detection limit, quantification limit, linearity ,accuracy, robustness and range. The linearity of the method was confirmed over the range of 0.113 to 3.384µg/ml for Sitagliptin Phosphate impurities with correlation coeffients greater than r=0.999.The accuracy of the method was found to be 98.5 to 101.1% and %RSD as found to be less than 2% indicating high degree of accuracy and precision for the proposed method. The effective recovery and lower RSD proves the highness of the proposed RP HPLC method for the routine determination of Sitagliptin Phosphate impurities in drug substances.