Owing to underlying diseases and decreased physiological functions, frailty in elderly patients may be associated with adverse postoperative complications and mortality. To date, there are various frailty assessment methods, with the five-item modified frailty index (mFI-5) being an objective and concise evaluation tool. This study aimed to clarify whether mFI-5 scoring, a measure of frailty, can predict postoperative outcomes in elderly patients undergoing laparoscopic colorectal surgery. A total of 107 patients aged over 80 years who underwent laparoscopic colorectal surgery at Nagasaki University Hospital between 2011 and 2018 were included in this study. The mFI-5 was used to assess the preoperative condition of each patient, with scores compared against various postoperative outcome measures. Univariate analysis was used to determine between-group differences for pre- and post-operative variables. Of the 107 patients [median age, 83 (80-99) years], 44.9% were male. The mFI-5 score was calculated and patients were divided into three groups: 0 (n=36, 33.6%); 1 (n=44, 41.1%); and 2+ (n=27, 25.3%). The groups were significantly associated with the American Society of Anesthesiology (ASA) classification (p<0.001). Postoperative complications occurred in 43 patients (40.2%), and a higher mFI-5 score was significantly associated with postoperative complications of Clavien-Dindo grade ≥III and duration of hospital stay. The mFI-5 is an objective and useful tool for predicting postoperative complications of laparoscopic surgery in elderly patients with colorectal cancer.