Colon is a crucial partner for small intestinal adaptation and function in patients who underwent extensive small intestinal resection or transplantation. This short review deals with the different properties and roles of the colon in these settings, involving fluid and electrolytes absorption, absorption of medium-chain triglycerides, and production of short-chain fatty acids for malabsorbed energy salvage. The colon may adapt after small intestinal resection, whereas it hosts the most important part of the intestinal microbiota, which plays a crucial role in intestinal function and health. Also, colon may be responsible for D-lactic acidosis as well, as it can be injured by noninfectious colitis. Finally, the relevance of a simultaneous colon grafting is discussed as it is occasionally considered in specific patients requiring intestinal transplantation.