Objective To evaluate the effect of preoperative intake of oral nutritional supplements (ONS) in gastrointestinal cancer patients at high risk of malnutrition, and to promote prehabilitation. Methods A convenient sample of 103 gastrointestinal cancer patients at nutritional risk and candidate to major surgery was assigned to a control group of 52 or an intervention group of 51 according to the wards where they were treated.The control group received routine preoperative nutrition management following enhanced recovery after surgery protocols, while the intervention group were administered a standard ONS.Nutritional status, out-of-bed mobilization time and gastrointestinal function between the two groups were compared. Results Forty-seven patients in the control group and forty-six in the intervention group completed the study.Both groups had lower values of serum albumin, prealbumin, and retinol-binding protein on postoperative day 3 than admission （all P＜0.05）.The intervention group had significantly higher serum albumin and prealbumin level on postoperative day 3 compared with the control group (both P＜0.05). Time to first ambulation, flatus, faeces, and fluid intake in the intervention group were significantly shortened than the control group （all P＜0.05）. Conclusion A preoperative nursing intervention with ONS improves postoperative nutritional status and recovery of patients with gastrointestinal neoplasm.