<p>The aim of this study was to analyze the factors contributing to the development of pneumonia after colorectal cancer (CRC) surgery and to develop a validated nomogram to predict the risk. We retrospectively collected information on patients who underwent radical CRC resection at a single clinical center from January 2011 to December 2021. The information was then randomly assigned to a training cohort and a validation cohort in a 7:3 ratio. Univariate and multivariate logistic regression analysis were performed on the training cohort to identify independent risk factors for the development of pneumonias, which were then included in the nomogram. Validation was performed in a validation cohort, area under the curve (AUC) and calibration curves were used to determine the predictive accuracy and discriminative power of the graphs, and decision curve analysis (DCA) was used to further substantiate the clinical efficacy of the nomogram. A total of 7130 patients were included in the study. Based on multivariate logistic regression analysis of the training cohort, age, sex, preoperative albumin, surgical methods, and surgical time were identified as independent risk factors for the development of pneumonia after CRC surgery, and a nomogram prediction model was established using the above five variables. The AUC was 0.745 in training cohort and 0.773 in validation cohort. This study established a nomogram that is a good predictor of the risk of developing pneumonia after CRC surgery and provided surgeons with a reference for personalized management of patients in the perioperative period.</p>