A 5-year-old female spayed Domestic Shorthair cat presented to the Cornell University Hospital for Animal's Soft Tissue Surgery Service on 7 /28/15 for further evaluation of previously diagnosed megacolon. In April 2014, the patient first started showing signs of constipation, lethargy, and passing oversized feces. Throughout the following months, these conditions progressed in severity, despite medical management with lactulose, cisapride, and a high-fiber/high-moisture diet prescribed by her local veterinarian. The weeks immediately preceding the consultation at Cornell, the patient was having weekly appointments at her local veterinarian for deobstipation and enemas under sedation. On presentation to Cornell, the patient's physical examination was unremarkable, except for a moderate amount of very firm fecal material distending the large intestine. On abdominal palpation, the proximal two-thirds of the descending colon was subjectively measured at approximately 4 cm in diameter. Radiographs and an abdominal ultrasound were performed under sedation for further diagnostic evaluation and surgical planning. Intra-abdominal exploratory laparotomy under general anesthesia revealed that the entire colon (namely ascending, transverse, and descending segments) was affected. The remainder of the abdomen and organs were subjectively normal upon visualization and palpation. Subtotal colectomy with colocolonic anastomosis, leaving the ileocecocolic junction intact proximally, was performed following standard aseptic surgical technique. Recovery from surgery was uneventful and the feline patient was maintained in the ICU on Plasmalyte, dexmedetomidine, ampicillin, metronidazole, buprenorphine, and lactulose. At one day post-operatively, intravenous fluids and medications were tapered and discontinued, and the patient was discharged to the care of her owners with prescribed buprenorphine and lactulose solution. This paper will focus on diagnosis of idiopathic megacolon, medical management treatment options for this condition, and a detailed approach of surgical management through subtotal colectomy. Also, a review of the anatomy and physiology of the feline colon will be briefly discussed.