Tele-intensive care unit (ICU) is a care provided to critically ill patients by off-site clinicians using audio, video, and electronic links to leverage technical, informational, and clinical resources. Providing care includes the ability to detect patient's instability or laboratory abnormalities in real-time, collect additional clinical information from or about the patient, order diagnostic testing, make diagnoses, implement treatment, render other forms of intensive care such as managing life-support devices, and communicate with patients and bedside providers. This review summarizes how tele-ICU services are delivered, the alternative approaches that have been used, and summarizes published reports of its effects on patient-focused outcomes. Tele-ICU is thought to have great promise to support critically ill adults.