ObjectiveThis study aimed to construct a nomogram to effectively predict the 3 years and 5 years overall survival of patients with thymic squamous cell carcinoma (TSCC).MethodFrom 2000 to 2019, a total of 355 patients with TSCC were enrolled in our research from the Surveillance, Epidemiology, and End Results (SEER) database and used as the training cohort. 106 patients were included from the Zhejiang Cancer Hospital, for the external validation cohort. A nomogram was constructed based on the risk factors affecting prognosis using a Cox proportional hazards regression model. The discrimination and calibration of the nomogram were evaluated by C-index and curve of calibration. The two cohorts were divided into low-risk and high-risk subgroups based on the median risk score.ResultsAge (p= 0.002), stage (p=0.003), surgery therapy(p<0.001), and radiotherapy (p= 0.030) were the independent prognostic factors for overall survival and were incorporated in the prognostic model. The discrimination of the nomogram revealed a good prognostic accuracy and clinical applicability as indicated by C-index values of 0.696 (95% confidence interval [CI] 0.676–0.716) and 0.717 (95% CI 0.640–0.794) for the training cohort and external validation cohort, respectively. In addition, the two cohorts were divided into a high-risk group and a low-risk group according to the median risk score. Significant differences in overall survival were observed between the high-risk and low-risk groups in the training (p< 0.0001) and external validation cohort (p< 0.0001).ConclusionWe developed a nomogram to predict 3- and 5 year survival rate for TSCC. This nomogram provides a convenient and reliable tool for assessing the condition of patients with TSCC and assisting clinicians in making decisions.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12672-023-00720-4.