Background: High-dose chemotherapy followed by autologous stem cell transplantation (HDC/ASCT) is standard of care for patients with diffuse large B-cell lymphoma (DLBCL) whose diseases relapse after, or are refractory to, first-line therapy. However, there are still high rates of relapse following ASCT, and non-relapse mortality also affects survival rates. Prognostic indicators are therefore needed to identify the best candidates for HDC/ASCT. Methods: We retrospectively analyzed medical records of 111 DLBCL patients (78 relapsed, 33 refractory) who underwent HDC/ASCT at the University of California Los Angeles from 2010-2015. Results: The median age at the time of ASCT was 61 years (IQR 51.5-68.0). 80 patients (72%) had DLBCL in a complete response at the time of ASCT, and the majority (98 patients, 88%) had ECOG performance status of 0-1. After a median follow-up of 4.6 years (IQR 2.2-8.1), the 1-year progression-free survival (PFS) rate was 77.3% (95% CI 69.7%-85.7%) and the 1-year overall survival (OS) rate was 84.7% (95% CI 78.2%-91.7%). 41 patients (37%) relapsed after ASCT with a median PFS of 11 months (IQR 5.0-20.0). 37 patients (33%) died, 23 (21%) from relapse mortality, 11 (10%) from non-relapse mortality, and 3 (3%) from unknown cause of death. In univariate analysis, 2 variables were significantly associated with curtailed PFS and OS: higher number (≥ 3 vs < 3) of chemotherapy regimens prior to ASCT (HR 2.20, 95% CI 1.19-4.06, p = 0.013 for PFS; HR 2.01, 95% CI 1.06-3.84, p = 0.036 for OS) and higher International Prognostic Index (IPI) score at time of ASCT (trend HR 1.61, 95% CI 1.10-2.35, p = 0.018 for PFS; trend HR 2.02, 95% CI 1.37-2.98, p = 0.001 for OS). Higher National Comprehensive Cancer Network (NCCN) IPI score at time of ASCT (trend HR 2.29, 95% CI 1.34-3.90, p = 0.002) and refractory versus relapsed disease (HR 1.99, 95% CI 1.04-3.82, p = 0.038) were also significantly associated with curtailed OS. Conclusions: Our study suggests that IPI, while a validated prognostic tool at diagnosis, is also a prognostic indicator at time of ASCT for PFS and OS. NCCN IPI at time of ASCT was also found to be predictive of OS. Age-adjusted IPI was not associated with outcome following ASCT.