The process related impurity of Nifedipine diethyl 1, 4-dihydro-2, 6-dimethyl pyridine 3, 5 dicarboxylate in bulk and formulations was synthesized. The characterization of synthesized impurities by using FTIR, NMR and MS. The RP-HPLC method was developed according to ICH Q2B guidelines for quantitation of impurity in bulk and formulations. The method was validated as per ICH guidelines. The method was found to be linear, precise, accurate, robust and rugged. The diethyl 1,4-dihydro-2,6- dimethyl pyridine 3,5 dicarboxylate impurity was quantified from bulk Nifedipine and its marketed tablet formulations. It was revealed that the amount of impurity present in tablet batch I and II was found to be 0.26% and 0.32% respectively and the bulk was found to be negligible.