To facilitate decision-making support for individual patients, development and external validation of a nomogram was undertaken to reveal prognostic factors and predict the value of concurrent chemoradiotherapy (CCRT) compared with radiotherapy (RT) for stage-II nasopharyngeal carcinoma (NPC) patients. Clinical data of 419 and 309 patients with American Joint Committee on Cancer (2017) stage-II NPC in two institutions in China were collected retrospectively. Overall survival (OS) and progression-free survival were compared using Kaplan-Meier estimates. Cox regression analysis was used to identify the prognostic factors for building the nomogram. Predictive accuracy and discriminative ability were measured using the Concordance Index. Finally, there were 24 and 20 deaths in the development and validation group, respectively. Patients with stage T2N1, N1 stage, involvement of retropharyngeal and unilateral cervical lymph nodes, and who had RT alone had worse OS (=0.019, 0.035, 0.003 and 0.010, respectively; log-rank test) than patients with stage T1N1 and T2N0, N0 stage, involvement of retropharyngeal or unilateral cervical lymph nodes, and CCRT, respectively. After multivariate analysis of the training set, age, neutrophil-to-lymphocyte ratio, therapy type, and pretreatment plasma concentration of Epstein-Barr virus DNA were independent prognostic factors of OS. A nomogram was established externally by involving all the factors stated above. The Concordance Index for the established nomogram to predict the OS of the training set was 0.793 (95% CI 0.689-0.897), and 0.803 (95% CI 0.696-0.910) in the validation set. These data suggest that the nomogram was validated externally, could predict long-term outcome accurately, and enable accurate stratification of risk groups for stage-II NPC. Our model facilitated individualized care of NPC patients.