Introduction: Regular dialysis, is not able to maintain phosphorus in the normal range. Therefore, using phosphate chelators to keep serum level of phosphorus in the normal range is essential. Sevelamer is a chelator for phosphate. Objectives: The purpose of this investigation was to compare the therapeutic impact of sevelamer carbonate versus sevelamer hydrochloride on electrolytes and metabolic acidosis and gastrointestinal symptoms in a group of hemodialysis patients. Patients and Methods: In this randomized clinical trial, patients were divided into two treatment groups; sevelamer carbonate and sevelamer hydrochloride. Sevelamer carbonate and sevelamer hydrochloride were prescribed as daily 800 mg tablets three times daily with their meals. Patients were evaluated for serum calcium, phosphorus, plasma bicarbonate and pH levels after one month. Results: Around 44 patients were enrolled, of which 22 patients were treated with sevelamer hydrochloride and 22 patients in the intervention group with sevelamer carbonate. There was no significant difference between the effects of sevelamer carbonate and sevelamer hydrochloride on serum calcium and phosphorus levels at the end of the study (P>0.05). There was a significant difference between the effects of sevelamer carbonate versus sevelamer hydrochloride on plasma bicarbonate and pH levels (P=0.036 and P=0.012 respectively). In terms of gastrointestinal complications, two drugs did not differ significantly. Conclusion: To prevent acidosis, along with increasing plasma bicarbonate and blood pH in patients undergoing hemodialysis, sevelamer carbonate is better than sevelamer hydrochloride. Therefore, the administration of sevelamer hydrochloride is preferable. Trial Registration: The trial protocol was approved by the Iranian Registry of Clinical Trials (identifier: IRCT20141016019554N13, https:// en.irct.ir/trial/28916, ethical code#IR.ZUMS.REC.1397.352).