Aim: The aim of this study was to determine the effect of perioperative immunonutrition on nutritional status, body composition, inflammatory profile, and postoperative outcomes in patients with nonmetastatic colorectal cancer. Subjects and Methods: A prospective study was conducted and included 76 patients planned for elective surgery for non-metastatic colorectal cancer. All were treated at the Surgery Department of University Hospital Split in the period from March 20, 2020 to May 5, 2021 in accordance with the protocol of enhancedrecovery after surgery (ERAS). Data were collected by searching patient history records, bioimpedance scale software (Tanita, MC-780 MA), and nutritional risk assessment questionnaires (NRS 2002). Results: In this study, more patients had an improvement in nutritional status in the group that received oral nutritional support longer than those that received shorter. Of the total number of patients, after completing the nutritional intervention, 18.05% of patients had a lower nutritional screening score compared to the initial nutritional screening. Total protein, albumin, and hemoglobin decreased after surgery in both groups of patients receiving oral nutritional support, and CRP and leukocytes increased. The difference in these parameters was more pronounced in the group receiving shorter course of nutritional support. Furthermore, a lower number of postoperative complications were found in the group that received oral immunonutrient support for a longer period of time, and in the same group there was a shorter length of hospitalization. In this study, a significant negative correlation was observed between the phase angle and the proportion of extracellular in total body fluid in all patients. Conclusion: Nutritional intervention led to an improvement in nutritional status in 18.05% of patients. The difference in the values of inflammatory parameters before and after surgery was more highlighted in the group in which the nutritional intervention lasted shorter. In the group that received oral nutritional support for longer period, there were fewer postoperative complications and the length of hospitalizations was shorter.