Objective: To compare the prognostic factors of Siewert type II AEG patients who had received neoadjuvant radiotherapy (nRT) versus those who did not receive nRT. Nomograms for outcome prediction were constructed for the two treatment modalities. Materials and methods: Data for 1,745 Siewert II type AEG patients who underwent radical surgery between 2010 and 2015 were retrieved from SEER (Surveillance, Epidemiology, and End Results) database. Patients were assigned to neoadjuvant radiotherapy (nRT) and non-neoadjuvant radiotherapy (non-nRT) groups based on treatment modality. Independent prognostic predictors were used to develop nomograms. Concordance index (C-index), receiver operating characteristic (ROC), calibration curves, and decision curve analyses (DCA) were used to determine the performance and prognostic value of the nomograms. The predictive accuracy of nomograms was compared with the prognostic value of the Tumor-Node-Metastasis (TNM) staging system. Results: The results showed that age, lymph node rate (LNR), and the number of removed lymph nodes (RLN) were independent prognostic factors for CSS in the nRT group. Tumor size, tumor grade, T stage, LNR, and therapy type were independent prognosis factors for CSS in patients in the non-nRT group. The C-indices for the nomograms were 0.652 (95% CI, 0.614-0.690) and 0.663 (95% CI, 0.606-0.720) in the training and validation cohort, respectively, for the nRT group. C-indices for the nomogram in non-nRT group were 0.754 (95% CI, 0.723-0.785) and 0.747 (95% CI, 0.6880.800) for the training and validation cohorts, respectively. C-indices and ROC curves showed good predictive value compared with the TNM staging system in both groups. C-indices, as well as the AUC values of the nomograms and the TNM staging system for both cohorts in the non-nRT group were higher compared with those in the nRT group. Analysis of the survival calibration curve revealed high consistency between actual versus predicted outcomes determined by the nomograms. Decision curve analyses revealed that the new models had higher prediction value and clinical significance compared with TNM staging system. Conclusion: The established nomograms showed high prognostic value for Siewert type II AEG patients in both nRT and non-nRT groups. In addition, the nomogram and the TNM staging systems showed better prognostic performance for patients in the non-nRT group compared with patients in the nRT group.