AbstractObjectivesImproved survival after hematopoietic cell transplantation (HCT) and an increasingly comorbid transplant population may give rise to new trends in the causes of death.MethodsThis study includes all adult allogeneic HCT recipients transplanted at Rigshospitalet between January 1, 2010 and December 31, 2019. Underlying causes of death were determined using the Classification of Death Causes after Transplantation (CLASS) method.ResultsAmong 802 HCT recipients, 289 died during the study period. The main causes of death were relapse (N = 133, 46.0%), graft‐versus‐host disease (GvHD) (N = 64, 22.1%) and infections (N = 35, 12.1%). Multivariable analyses showed that with increasing transplant calendar year, a decreased risk of all‐cause mortality (HR 0.92, 95% CI 0.87–0.97) and death from GvHD (HR 0.87, 95% CI 0.78–0.97) was identified, but not for other specific causes.Standardized mortality ratios (SMRs) for all‐cause mortality decreased from 23.8 (95% CI 19.1–28.5) to 18.4 (95% CI 15.0–21.9) for patients transplanted in 2010–2014 versus 2015–2019, while SMR for patients who died from GvHD decreased from 8.19 (95% CI 5.43–10.94) to 3.65 (95% CI 2.13–5.18).ConclusionsAs risk of all‐cause mortality and death from GvHD decreases, death from relapse remains the greatest obstacle in further improvement of survival after HCT.