Cancer during pregnancy is relatively rare but is increasing in frequency in countries in which the maternal child-bearing age continues to rise. The complexities of medical decision making are underscored by the need to weigh the potential benefits of any intervention for the mother against the risks to the fetus. A majority of diagnostic evaluations can be performed safely in the setting of pregnancy and should not be delayed. Noninvasive prenatal testing that shows discordance with fetal karyotype can be a clue to an underlying maternal malignancy. After diagnosis, a multidisciplinary team should formulate a care plan for both the mother and the fetus. Key topics for discussion should include the mother's prognosis, standard treatment plan, and predictions of how modifications for a continuing pregnancy will affect the treatment plan and overall prognosis. In the context of this knowledge, frank discussions about pregnancy termination should be addressed with the patient, if appropriate. Selection of a plan for oncologic management in the case of a pregnant woman is based on the type of cancer, the tumor biology, and the tumor stage. Additional complexities for pregnant patients are typically related to the gestational age of the fetus, the dynamic physiologic changes of pregnancy, and the limited safety data for administration of most anticancer therapies during pregnancy. In this article, we summarize data related to different classes of anticancer therapies as well as considerations for the management of selected cancers. Finally, we provide some key principles that should be considered in the management of patients with cancer during pregnancy.