BACKGROUND: Very few studies have been conducted on the treatment strategy for enlarged paraaortic lymph nodes (PALNs) incidentally detected during surgery. The purpose of this study was to investigate the benefit of lymph node dissection in patients with incidentally detected enlarged PALNs. METHODS: We retrospectively reviewed patients with left colon and rectal cancer who underwent surgical resection with PALN dissection between January 2010 and December 2018. The predictive factors for pathologic PALN metastasis (PALNM) were analyzed, and survival analyses were conducted to identify prognostic factors. RESULTS: Among 263 patients included, 19 (7.2%) showed pathologic PALNM and 5 (26.33%) had enlarged PALNs incidentally detected during surgery. These 5 patients accounted for 2.2% of 227 patients who had no evidence of PALNM on preoperative radiologic examination. Radiologic PALNM (odds ratio [OR] 12.737, 95% confidence interval [CI] 3.472-46.723) and radiologic distant metastasis other than PALNM (OR = 4.090, 95% CI 1.011-16.539) were independent predictive factors for pathologic PALNM. Pathologic T4 stage (hazard ratio [HR] 2.196, 95% CI 1.063-4.538) and R2 resection (HR 4.643, 95% CI 2.046-10.534) were independent prognostic factors for overall survival (OS). In patients undergoing R0 resection, pathologic PALNM was not associated with 5-year OS (90% vs. 82.2%, p = 0.896). CONCLUSION: Dissection of enlarged PALNs incidentally detected during colorectal surgery may benefit patients with favorable survival outcomes.