Background/Aim: High-output ileostomy (HOI) can affect quality of life, however, its primary cause remains unknown. This study aimed to identify a predictor of HOI after colorectal surgery. Patients and Methods: The medical records of forty-five patients who had undergone colorectal surgery with temporary ileostomy without postoperative complications, such as intra-abdominal abscess, paralytic ileus, outlet obstruction, or suture rupture, at our hospital between January 2016 and December 2017 were retrospectively investigated. Results: Significant differences in age, gender, operative situation, duration of operation, intraoperative blood loss, operation procedure, operation approach, preoperative body mass index, and preoperative hematological/biochemical parameters, such as leucocyte counts, hemoglobin, serum total protein, albumin, C-reactive protein, and preoperative complications, were not identified between the two groups. Preoperative neutrophil-to-lymphocyte ratio (NLR) of the HOI group was significantly higher than that of the non-HOI group (p=0.004). Conclusion: Preoperative NLR seems to be a useful predictor of HOI after colorectal surgery.