Background Septic complications after colorectal surgery are frequent and sometimes life-threatening. It is well-known that inflammation impairs the healing process. It has been suggested that preoperative ongoing inflammation could increase the risk of postoperative infections. This study aimed to elucidate the role of preoperative inflammation on postoperative infectious complications and to understand if, through biological markers, it is possible to identify preoperatively patients at higher risk of infection. Methods A prospective, observational study was conducted in three centers from November 2011 to April 2014. Consecutive patients undergoing elective colorectal surgery with anastomosis were included. Any ongoing infection was an exclusion criterion. C-reactive protein, albumin, prealbumin and procalcitonin plasma levels were measured preoperatively. Postoperative infections were recorded according to the definitions of the Centers for Diseases Control. The areas under the receiver operating characteristic curve were analyzed and compared to assess the accuracy of each preoperative marker. Results Four-hundred and seventy two patients were analyzed. Infectious complications occurred in 118 patients (25%) and mortality in 6 patients (1.3%). In the univariate analysis, preoperative C-reactive protein and albuminemia were found significantly associated with postoperative infectious complications (P = 0.008 and P = 0.0002, respectively). Areas under the ROC curve for preoperative C-reactive protein and albuminemia were 0.57and 0.62, respectively. Conclusions This study confirms the association between preoperative inflammatory activity, hypoalbuminemia and the onset of infections after surgery. Trials aiming to decrease the inflammatory activity before surgery in order to prevent postoperative complications are warranted.