Background: Gallbladder cancer (GBC) has a poor prognosis. The aim was to develop and validate a preoperative risk score for incidental gallbladder cancer (IGBC) in patients scheduled for cholecystectomy. Methods: Data registered in the nationwide Swedish Registry for Gallstone Surgery (GallRiks) was analyzed, including the derivation cohort (n = 28915, 2007-2014) and the validation cohort (n = 7851, 2014-2016). An additive risk score model based on odds ratio was created. Results: The scoring model to predict IGBC includes age, female gender, previous cholecystitis, and either jaundice or acute cholecystitis. The calibration by HL test and discrimination by AUROC was 8.27 (P = 0.291) and 0.76 in the derivation cohort (214 IGBC) and 14.28 (P = 0.027) and 0.79 in the validation cohort (35 IGBC). The scoring system was applied to three risk-groups, based on the risk of having IGBC, eg. the high-risk group (>8 points) included 7878 patients, with 154 observed and 148 expected IGBC cases. Conclusion: We present the first risk score model to predict IGBC. The model estimates the expected risk for the individual patient and may help to optimize treatment strategies. (c) 2020 Elsevier Inc. All rights reserved.