AIM Whether reoperation in the postoperative period adversely affects oncologic outcomes for colorectal cancer patients undergoing resection has not been well characterized. The aim of this study was to determine whether long-term oncological outcomes are affected for patients who undergo repeat surgery in the early postoperative period. METHOD From a prospective colorectal cancer database, patients who underwent resection for colorectal cancer between 1982 and 2008 and were reoperated within 30 days after surgery (group A) were matched for age (±5 years), gender, year of surgery (±2 years), American Society of Anesthesiology score, tumor site (colon or rectum), cancer stage and differentiation with patients who did not undergo reoperation (group B). The two groups were compared for overall survival (OS), disease-free survival (DFS) and local recurrence (LR). RESULTS In total, 89 reoperated patients (45 rectal, 44 colon cancer) were matched to an equal number of non-reoperated patients. Anterior resection (39.2%) and right hemicolectomy (19.1%) were predominant primary operations. Indications for reoperation were anastomotic leak/abscess (n=40, 45%), massive bleeding (n=15, 16.9%), bowel obstruction (n=11, 12.4%), wound complications (n=9, 10.1%) and other indications (n=14, 15.6%). Group A had significantly greater overall morbidity (100% vs 27%, P=0.001) and required more blood transfusions (20.2% vs 7.9%, P=0.045). Adjuvant therapy use, on the other hand, was more common in group B (23.6% vs 12.3%, P=0.1). The 5-year OS and DFS were lower in the reoperated group (OS 55.3% vs 66.4%, P=0.02; DFS 50.8% vs 60.8%, P=0.06, respectively). Five-year LR was slightly lower in the reoperated group (2.9% vs 6.3%, P=0.34). CONCLUSIONS Compared with non-reoperated patients matched for patient, tumour and operative characteristics, patients reoperated in the early postoperative period have worse long-term oncological outcomes. Adoption of strategies to reduce the risk of reoperation may be associated with the additional advantage of improved oncological outcomes in addition to the short-term advantages.