Sevelamer is an important drug used to lower serum phosphate levels in advanced kidney disease and in patients on dialysis. This drug is generally well tolerated but some patients report mild gastrointestinal distress as a side effect. Although regulatory agencies, such as Food and Drug Administration, list bowel ischemia and necrosis as potential and rare side effects, there are few case reports describing these adverse effects. We present a 35-year-old HIV patient with end-stage renal disease on hemodialysis who developed colonic hemorrhage and perforation. Imaging showed ischemic gangrene of bowel wall. Histopathology was consistent with transmural ischemic necrosis with deposition of fibrin thrombi and sevelamer crystals.