During the early clinical course of cancer therapy, a significant percentage of patients are admitted to the intensive care unit due to cardiovascular complications of their disease, vascular access devices, and chemo- or immunotherapies. Critically ill oncologic patients require immediate evaluation, therapeutic intervention, and post-treatment monitoring. Transthoracic echocardiography is a noninvasive, real-time, fast, relatively cost-effective, and portable imaging modality that can give vital information to the clinical care team. Two-dimensional echocardiography can provide a detailed cardiac anatomical assessment, and Doppler echocardiography analysis of blood flow provides functional hemodynamic information. However, transthoracic echocardiographic imaging and its interpretation is technically challenging in the intensive care unit due to mechanical ventilation, surgical drains/wounds, and inadequate patient positioning. Clinical settings in which transesophageal echocardiography provides a more accurate diagnostic evaluation include critically ill patients with an inability to obtain diagnostic quality images with transthoracic echocardiography and patients evaluated for suspected valvular disease, intracardiac thrombus/masses, endocarditis, aortic dissection, and post-cardiac surgery tamponade. In this chapter, we aim to review the most common applications of transthoracic and transesophageal echocardiography in the oncologic intensive care unit.