Background Postoperative infectious complications (PICs) after gastric cancer resection remain a clinically relevant problem. Early detection of PICs, before critical illness develops, may be of considerable clinical benefit. The aims of this study were to investigate the predictive factors for PICs and to define the clinical parameters for detecting them early in patients with gastric cancer resection. Methods Clinical data for 417 consecutive patients undergoing elective gastrectomy for primary gastric cancer between 2009 and 2012 were retrospectively analyzed. Conclusions Elevated CRP levels on POD 3 will help physicians predict the postoperative course and facilitate decision-making regarding prompt, comprehensive clinical searches and therapeutic approaches for PICs.