Autologous hematopoietic stem cell transplantation (AHCT) improves survival in patients with multiple myeloma (MM) but is associated with morbidity and nonrelapse mortality (NRM). Hematopoietic cell transplant comorbidity index (HCT-CI) was shown to predict risk of NRM and survival after allogeneic transplantation. We tested the utility of HCT-CI as a predictor of NRM and survival in patients with MM undergoing AHCT. We analyzed outcomes of 1156 patients of AHCT after high-dose melphalan reported to the Center for International Blood and Marrow Transplant Research. Individual comorbidities were prospectively collected at the time of AHCT. The impact of HCT-CI and other potential prognostic factors, including Karnofsky performance score (KPS), on NRM and survival were studied in multivariate Cox regression models. HCT-CI score was 0, 1, 2, 3, and ≥3 in 42%, 18%, 13%, 13%, and 14% of the study cohort, respectively. Subjects were stratified into 3 risk groups: HCT-CI score of 0 (42%) versus HCT-CI score of 1 to 2 (32%) versus HCT-CI score ≥ 2 (26%). Higher HCT-CI was associated with lower KPS < 90 (33% of subjects score of 0 versus 50% in HCT-CI score ≥ 2). HCT-CI score ≥ 2 was associated with melphalan dose reduction (22% versus 10% in score 0 cohort). One-year NRM was low at 2% (95% confidence interval, 1% to 4%) and did not correlate with HCT-CI score (P= .9). On multivariate analysis, overall survival was inferior in groups with HCT-CI score of 1 to 2 (relative risk, 1.37, [95% confidence interval, 1.01 to 1.87], P= .04) and HCT-CI score ≥ 2 (relative risk, 1.5 [95% confidence interval, 1.09 to 2.08], P= .01). Overall survival was also inferior with KPS < 90 (P < .001), IgA subtype (P ≤ .001), those receiving ≥1 pretransplant induction regimen (P= .007), and those with resistant disease at the time of AHCT (P < .001). AHCT for MM is associated with low NRM, and death is predominantly related to disease progression. Although a higher HCT-CI score did not predict NRM, it was associated with inferior survival. © 2014 American Society for Blood and Marrow Transplantation.