Patients treated for a hematologic malignancy are at risk for treatment-related complications. As the goal of therapy is frequently curative, treatments are especially intensive and long-term toxicity is common. Chemotherapy and radiation are associated with increased risk for cardiac and pulmonary disease, endocrine disorders, infertility, sexual dysfunction, second cancers, and psychosocial distress. The risk for each complication is dictated by patient characteristics including age, co-morbidities, and genetic predispositions, as well as the specifics of therapy. Survivors of pediatric cancers and allogeneic hematopoietic stem cell transplantation have unique risks due to vulnerable age at time of toxic exposure and ongoing immune dysfunction, respectively.