Objective To construct and validate an effective prognostic nomogram for the patients with incidental gallbladder cancer(IGBC). Methods The clinical data of 161 patients with IGBC requiring radical surgery admitted to the First Affiliated Hospital of Xi’an Jiaotong University from May 2011 to October 2022 was analyzed retrospectively. COX proportional risk regression model was used to screen for influencing factors on overall survival(OS) of IGBC. Nomogram was constructed based on independent influencing factors that affected the prognosis of IGBC patients. The concordance index(C-index) and calibration curve were used to validate the performance of the model. Receiver operating characteristic (ROC) curve analysis and decision curve analysis (DCA) were used to validate the predictive accuracy and net benefit of the plotted column chart. Results Univariate COX regression analysis suggested that age, T stage, N stage, M stage, preoperative carcinoembryonic antigen(CEA), preoperative carbohydrate antigen19-9(CA19-9), preoperative red blood cell volume distribution on width coefficient of variation(RDW-CV), treatment method, and recurrence and metastasis were risk factors which affected the long-term survival of IGBC patients after radical surgery. Multivariate COX regression analysis suggested that T stage, N stage, preoperative CA19-9， preoperative RDW-CV, preoperative AST， treatment methods, and recurrence and metastasis were independent risk factors which affected the prognosis of IGBC patients. The C-index of the constructed prognostic model was 0.872. The calibration plot demonstrated good performance of the Nomogram. ROC curve analysis showed an area under the curve of 0.869, confirming a high sensitivity and specificity. A high net benefit was proven by DCA. Conclusions The constructed Nomogram can accurately and intuitively predict the survival probability of IGBC patients after radical surgery.