This study examined the clinical significance of very high preoperative carbohydrate antigen 19-9 (CA19-9) levels in patients with early-stage colorectal cancer (CRC). We retrospectively analyzed the clinicopathological data of patients who underwent curative resection for primary CRC (c-Stage I-III) between 2004 and 2022 in our facility. The patients were classified into three groups according to the preoperative CA19-9 level: normal (≤37.0 U/ml), high (>37.0 to ≤100.0 U/ml), and very high (>100.0 U/ml). Of 971 patients, 885 (91.1%), 67 (6.9%), and 19 (2.0%) had normal, high, and very high CA19-9 levels, respectively. Overall survival (very high vs. normal: p<0.0001, very high vs. high: p=0.01) and recurrence-free survival (very high vs. normal: p<0.0001, very high vs. high: p=0.18) were significantly worse in the very high group. On multivariate analysis including TNM stage, very high preoperative CA19-9 levels were independently associated with worse overall (odds ratio=4.54; 95% confidence interval=2.03-10.16; p=0.0002) and recurrence-free survival (odds ratio=3.49; 95% confidence interval=1.82-6.69; p=0.0002). High preoperative CA19-9 levels were associated with poor survival in early-stage CRC. Careful intraoperative observation and close follow-up might be necessary.