Optimal post-remission therapy for adolescents and young adults (AYAs) with Ph-negative acute lymphoblastic leukemia (ALL) in first complete remission (CR1) is not established. We compared overall survival (OS), disease-free survival (DFS), relapse, and non-relapse mortality (NRM) for patients receiving post-remission therapy on CALGB 10403 to a cohort undergoing myeloablative (MA) allogeneic hematopoietic cell transplantation (HCT) in CR1. In univariate analysis, OS was superior with chemotherapy compared to MA allogeneic HCT (3-year OS 77% vs. 53%, P < 0.001). In multivariate analysis, allogeneic HCT showed inferior OS (HR 2.00, 95% CI 1.5–2.66, P < 0.001), inferior DFS (HR 1.62, 95% CI 1.25–2.12, P < 0.001), and increased NRM (HR 5.41, 95% CI 3.23–9.06, P < 0.001) compared to chemotherapy. A higher 5-year relapse incidence was seen with chemotherapy compared to allogeneic HCT (34% vs. 23%, P = 0.011). Obesity was independently associated with inferior OS (HR 2.17, 95% CI 1.63–2.89, P < 0.001), inferior DFS (HR 1.97, 95% CI 1.51–2.57, P < 0.001), increased relapse (1.84, 95% CI 1.31–2.59, P < 0.001), and increased NRM (HR 2.10, 95% CI 1.37–3.23, P < 0.001). For AYA ALL patients in CR1, post-remission therapy with pediatric-style chemotherapy is superior to MA allogeneic HCT for OS, DFS, and NRM.