Purpose: While the amylase concentration of the drainage fluid (dAmy) has been reported to be a predictor of postoperative pancreas-related complications (PPRC), the optimal timing for its measurement has not been fully investigated. Materials and Methods: The clinicopathological data of 387 patients who underwent elective gastrectomy for gastric cancer were reviewed. Laboratory data, including dAmy on postoperative days 1 (dAmy1) and 3 (dAmy3), and serum C-reactive protein (sCRP) concentrations on postoperative days 1 (sCRP1) and 3 (sCRP3) were compared between patients with PPRC and without PPRC. Results: Nineteen of the 387 patients (4.9%) developed PPRC. The optimal cutoff values of dAmy1, dAmy3, sCRP1, and sCRP3 were 1514 IU/L, 761 IU/L, 8.32 mg/dL, and 15.15 mg/dL, respectively. The area under the curve of dAmy1 was greater than that of dAmy3 (0.915 vs.0.826), and that of sCRP3 was greater than that of sCRP1 (0.820 vs. 0.659). In the multivariate analysis, dAmy1 (P<0.001) and sCRP3 (P=0.004) were significant predictors of PPRC, while dAmy3 (P=0.069) and sCRP1 (P=0.831) were not. Thirteen (41.9%) of 31 patients with both dAmy1 ≥1,545 IU/L and sCRP3 ≥15.15 mg/dL had PPRC ≥Clavien-Dindo II. In contrast, among 260 patients with both dAmy1 <1,545 IU/L and sCRP3 <15.15 mg/dL, none developed PPRC. Conclusions dAmy1 was more useful than dAmy3 in predicting PPRC. The combination of dAmy1 and sCRP3 may be a useful criterion for the removal of drains on postoperative day 3.