Oncologic therapy including chemotherapy and radiation can have a significant impact on ovarian function for young women and girls. Poor health outcomes and loss of fertility are major considerations. The effect of radiation and chemotherapy on ovarian function varies depending on patient age, therapy type and dosage, and cancer type. Surgical and medical interventions are available to reduce the morbidity of premature ovarian failure associated with cancer-directed therapy. Fertility preservation is an important consideration, and several options are available for it; therefore, early consultation with a reproductive or oncofertility specialist is an essential part of oncologic care in young women or girls. This chapter will focus on the effects of radiation and chemotherapy on ovarian function and strategies to improve the reproductive care in women with cancer.