Hematopoietic cell transplantation (HCT) provides a life-prolonging or potentially curative treatment option for patients with hematologic malignancies. Given the high transplant-related morbidity, these treatment strategies were initially restricted to younger patients, but are increasingly being used in older adults. The incidence of most hematologic malignancies increases with age; with the aging of the population, the number of potential older candidates for HCT is increasing. Autologous HCT (auto-HCT) in older patients may confer a slightly increased risk of specific toxicities (such as cardiac toxicities and mucositis) and have modestly lower effectiveness (in the case of lymphoma). However, auto-HCT remains a feasible, safe, and effective therapy for selected older adults with multiple myeloma and lymphoma. Similarly, allogeneic transplant (allo-HCT) is a potential therapeutic option for selected older adults, although fewer data exist on allo-HCT in older patients. Based on currently available data, age alone is not the best predictor of toxicity and outcomes; rather, the comorbidities and functional status of the older patient are likely better predictors of toxicity than chronologic age in both the autologous and allogeneic setting. A comprehensive geriatric assessment (CGA) in older adults being considered for either an auto-HCT or allo-HCT may identify additional problems or geriatric syndromes, which may not be detected during the standard pretransplant evaluation. Further research is needed to establish the utility of CGA in predicting toxicity and to evaluate the quality of survival in older adults undergoing HCT.