Megacolon is a disorder characterized by hypomotility and dilation of the colon. It is largely idiopathic in cats but can also be caused by chronic constipation due to obstruction. The most common cause of obstrnction leading to megacolon in cats is pelvic fracture malunion. Medical management of constipation includes the use of prokinetic agents, laxatives and special diets. When medical management is unsuccessful, surgical treatment is an excellent alternative. The purpose of this case report is to describe the use of a subtotal colectomy to treat chronic constipation and megacolon in a 5-year-old female spayed Domestic Shorthair cat with a history of a pelvic fracture malunion.