We evaluated the effects of the oral nutritional supplement containing arginine, glutamine, and hydroxymethylbutyrate (Abound®) on healing of colonic anastomoses in experimental rat model. Seventy WistarAlbino male rats were divided into seven groups. Colon transection and anastomosis were performed in all groups except for the sham group. In groups 2 and 5, rats were fed with standard rat chow after the operation. Oral nutritional supplement was added to standard nutrition for 3 days postoperatively in group 3 and 7 days in group 6 and preoperative 7 days plus postoperative 3 days in group 4 and preoperative 7 days plus postoperative 7 days in group 7. Bursting pressures were measured, adhesions were evaluated, and tissue samples were taken for measurement of tissue hydroxyproline levels and for histopathological examination. The usage of oral nutritional supplement had positive effects on bursting pressures, tissue hydroxyproline levels, and histopathological findings of anastomoses, but feeding with oral nutritional supplement both preoperatively and postoperatively had no additive effect on these parameters when compared with the groups that were fed only postoperatively. The mixture of arginine, glutamine, and hydroxymethylbutyrate may be safely used for achieving better healing results after colonic anastomoses.