Abstract We examined the association between risky health behaviors (smoking, heavy alcohol consumption, and lack of vigorous physical activity) and all-cause and cause-specific late mortality after blood or marrow transplantation (BMT) to understand the role played by potentially modifiable risk factors. Study participants were drawn from the BMT Survivor Study (BMTSS) and included patients who received transplantation between 1974 and 2014, had survived ≥2 years after BMT, and were aged ≥18 years at study entry. Survivors provided information on sociodemographic characteristics, chronic health conditions, and health behaviors. National Death Index was used to determine survival and cause of death. Multivariable regression analyses determined the association between risky health behaviors and all-cause mortality (Cox regression) and nonrecurrence-related mortality (NRM; subdistribution hazard regression), after adjusting for relevant sociodemographic, clinical variables and therapeutic exposures. Overall, 3866 participants completed the BMTSS survey and were followed for a median of 5 years to death or 31 December 2021; and 856 participants (22.1%) died after survey completion. Risky health behaviors were associated with increased hazard of all-cause mortality (adjusted hazard ratio [aHR] former smoker, 1.2; aHR current smoker, 1.7; reference, nonsmoker; aHR heavy drinker, 1.4; reference, nonheavy drinker; and aHR no vigorous activity, 1.2; reference, vigorous activity) and NRM (aHR former smoker, 1.3; aHR current smoker, 1.6; reference, nonsmoker; aHR heavy drinker, 1.4; reference: nonheavy drinker; and aHR no vigorous activity, 1.2; reference, vigorous activity). The association between potentially modifiable risky health behaviors and late mortality offers opportunities for development of interventions to improve both the quality and quantity of life after BMT.