Background/aims: We performed a prospective randomized clinical trial to evaluate the effects of preoperative one week enteral nutrition (EN) support on the postoperative nutritional status, immune function and inflammatory response of colorectal cancer patients. Materials and Methods: 96 patients undergoing colorectal surgery were randomly divided into preoperative one week EN group (trial group, n=48) and preoperative normal food group (control group, n=48). The EN group was continuously treated with EN support for 7 days according to the treatment protocols before operation. The control group was given normal food. All the patients were checked for their body weight, upper arm circumference, white blood cell count (WBC), albumin (ALB), prealbumin (PA), C-reactive protein (CRP), humoral immunity (IgA, IgG), T cell subsets (CD4, CD8 and CD4/CD8), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) on the preoperative and the postoperative 1st and 7th day, respectively. Results: PA and IgG levels of the experimental group were higher than those of the control group on the postoperative 7th day, whereas IL-6 level of the experimental group was lower than that of the control group. Conclusion: Preoperative one week EN support for colorectal cancer patients will improve the postoperative nutritional status and immune function, alleviate inflammatory response of colorectal cancer patients.