AbstractBackgroundThe establishment of precise and personalized prediction systems for chondroblastic osteosarcoma patients is important for guiding the treatment.MethodsThe univariate logrank test and multivariate Cox regression analysis were performed to identify independent prognostic factors for overall survival (OS) and cancer‐specific survival (CSS). Nomograms were constructed to estimate the OS and CSS based on these factors. Internal and external validation was performed. The predictive power of the nomograms was determined by C‐index and calibration plots.ResultsA total of 401 chondroblastic osteosarcoma cases were identified. Univariate and multivariate analysis revealed that age at diagnosis, histological grade, tumor size, Surveillance, Epidemiology, and End Results stage, and surgical resection were independent prognostic factors for OS and CSS. The five factors were incorporated to construct the nomograms for estimating the 3‐ and 5‐year OS and CSS. The C‐index values for the internal validation of the OS and CSS nomogram were 0.732 and 0.746, respectively, and for the external validation were 0.780 and 0.808, respectively. The calibration curves revealed that the predicted OS and CSS could well match the actual survival rate.ConclusionsThe nomograms for predicting 3‐ and 5‐year OS and CSS were constructed and were proved to be accurate and reliable by the internal and external validation.