Sodium polystyrene sulfonate (SPS) powder is in use for over 50 years for the treatment of hyperkalemia. SPS powder is official in United States Pharmacopoeia, British Pharmacopoeia and European Pharmacopoeia. However, till date, no study has been published on the assessment of organic impurities for this drug. The organic impurities in bulk drug and finished product are associated with their safety, efficacy and stability. A simple, rapid, specific, precise and an accurate HPLC method has been developed for the estimation of toxic organic impurities like styrene, naphthalene, divinyl benzene (DVB) and ethylvinyl benzene (EVB) from SPS bulk drug and finished product. The developed method was validated for specificity, accuracy, precision, linearity, limit of detection (LOD), limit of quantitation (LOQ), solution stability, ruggedness and robustness. The influence of acid, alkali, oxidative stress, photolytic stress, thermal stress and humidity stress conditions on SPS bulk powder and finished product has been studied and reported. The proposed method can be successfully employed for the impurity testing of commercial batches of the bulk drug and finished products of both sodium salt and calcium salt of polystyrene sulfonate.