Abstract Objective This 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). Method From 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. Results Age (p = 0.002), stage (p = 0.003), surgery therapy (p