The present paper describes about highly specific, linear, precise, rugged, accurate, robust and stability indicating RP-HPLC method for determination of related substances present in rufinamide tablets. Chromatographic separation with separation of impurities at satisfactory level was achieved using Inertsil ODS-3V (250 × 4.6 mm, 5 μm) column by using gradient elution mode. Mobile phase-A consists of 0.1% v/v triethylamine in water. pH adjusted to 2.2 with orthophosphoric acid. Mixture of 980 ml of methanol and 20 ml of tetrahydrofuran was used as Mobile phase-B. Flow rate was kept at 1.0 ml/min with a monitoring wavelength of 215 nm. Developed method was successfully validated as per method validation parameters recommended by International Conference on Harmonisation (ICH) for specificity, LOQ, LOD, linearity, precision, accuracy, robustness and solution stability. The validated Reverse phase-High Performance Liquid Chromatography (RP-HPLC) method was successfully used for quantitative determination of related substances of present and stability batches of rufinamide tablets.