Background: Testicular seminoma is the most common solid tumor seen in patients aged 15-35 and disease specific survival approaches 100% in controlled studies, even for those with node-positive disease. We sought to describe modern practice patterns as well as survival outcomes and factors associated with receipt of adjuvant therapy for patients presenting with initial clinical stage (CS) IIA/B disease. Methods: Data on patients diagnosed with CS IIA/B testicular seminoma from 1998-2011 were extracted from the National Cancer Data Base. Demographic, clinical, treatment, payer characteristics were evaluated using multivariate logistic regression to identify factors associated with receipt of chemotherapy or adjuvant radiation therapy (ART) within 6 months of orchiectomy. Five-year Kaplan-Meier overall survival (OS) by CS and treatment was calculated. Results: In total, 2,185 patients with CS II A/B were included. Management included orchiectomy alone (11.35%), adjuvant chemotherapy (27.46%), or ART (52.72%). In multivariate analysis, receipt of orchiectomy plus ART rather than adjuvant chemotherapy was more likely with CS IIA status (OR 2.4, p < 0.01), treatment outside of teaching or NCI network institution (OR 1.9-2.8, p < 0.02), or tumor size ≥4cm (OR 1.6, p < 0.01). Receipt of ART was less likely in Hispanic patients (OR 0.6, p=0.03) or in those diagnosed from 2006-2011 (OR 0.5, p < 0.01). Five-year OS for all patients was 97.2% for orchiectomy + ART, and 93.9% for orchiectomy + chemotherapy (log-rank p = 0.01). For CS IIA patients, 5-year OS was 98.3% for orchiectomy + ART versus 93.6% for orchiectomy + chemotherapy (log-rank p < 0.01). Differences in OS for CS IIB treated with chemotherapy or ART were not statistically significant. Conclusions: Consistent with national guideline recommendations, our analysis suggest that compared to chemotherapy, ART is associated with a survival advantage for CS IIA patients. Chemotherapy or ART showed no significant difference in effectiveness in patients with CS IIB. Disease bulk, race, treatment center type, and time period are associated with choice of adjuvant therapy. Longer follow-up and validation of these results is needed to account for late effects of treatment.