A simple, sensitive and reproducible Reverse phase high performance liquid chromatography (HPLC) coupled with a photodiode array detector; method was developed for the quantitative determination of related substances in API. Chromatographic separation was achieved on Hypersil ODS (125 X 4.0) mm, 5μm, and the gradient eluted with runtime, 50.0 min. The eluted compounds were monitored at 290 nm, the flow rate was 1.0 mL/min, and the column oven temperature was maintained at 40oC. The resolution of Pantoprazole and three impurities was greater than 2.0 for all pairs of components. The high correlation coefficient (r2> 0.9990) values indicated clear correlations between the investigated compound concentrations and their peak areas within the test ranges. The repeatability and intermediate precision, expressed by the RSD, were less than 10%. The accuracy evaluated by performing recovery studies via a spike method, was in the range 80.0-120.0%. The performance of the method was validated according to the present ICH guidelines for specificity, limit of detection, limit of quantification, linearity, accuracy, precision, ruggedness and robustness.