Targeted cancer therapies involve chemotherapeutic agents that attack, directly or indirectly, a specific genetic biomarker found in a given cancer. Targeted oncology includes monoclonal antibodies, small molecule inhibitors, antibody-drug conjugates, and immunotherapy. For example, the monoclonal antibodies trastuzumab and pertuzumab target human epidermal growth factor receptor 2 (HER2) and are used when treating HER2-positive breast cancer. Although targeted oncology has improved survival by years for some incurable cancers such as metastatic breast and lung cancer, as few as 8% of patients with advanced cancer qualify for targeted oncology medications, and even fewer benefit. Other limitations include serious adverse events, illustrated by a 20% to 30% rate of heart attack, stroke, or peripheral vascular events among patients taking ponatinib, which is used in treating chronic myelogenous leukemia. Immune checkpoint inhibitor therapy-related adverse effects such as hypothyroidism are common, and more severe adverse events such as colitis and pneumonitis can be fatal and require immediate intervention. Drug interactions with widely prescribed medications such as antacids and warfarin are common. Additionally, financial toxicities are a problem for patients with cancer who are using costly targeted therapies. Future directions for targeted oncology include tumor-agnostic drugs, which target a given mutation and could be used in treating cancers from multiple organ types. An overview of indications, mechanism of action, and toxicities of targeted cancer therapies is offered here.