Virtual reality (VR) and augmented reality (AR) are aspiring, new technologies with increasing use in critical care medicine. While VR fully immerses the user into a virtual three-dimensional space, AR adds overlaid virtual elements into a real-world environment. VR and AR offer great potential to improve critical care medicine for patients, relatives and health care providers. VR may help to ameliorate anxiety, stress, fear, and pain for the patient. It may assist patients in mobilisation and rehabilitation and can improve communication between all those involved in the patient's care. AR can be an effective tool to support continuous education of intensive care medicine providers, and may complement traditional learning methods to acquire key practical competences such as central venous line placement, cardiopulmonary resuscitation, extracorporeal membrane oxygenation device management or endotracheal intubation. Currently, technical, human, and ethical challenges remain. The adaptation and integration of VR/AR modalities into useful clinical applications that can be used routinely on the ICU is challenging. Users may experience unwanted side effects (so-called "cybersickness") during VR/AR sessions, which may limit its applicability. Furthermore, critically ill patients are one of the most vulnerable patient groups and warrant special ethical considerations if new technologies are to be introduced into their daily care. To date, most studies involving AR/VR in critical care medicine provide only a low level of evidence due to their research design. Here we summarise background information, current developments, and key considerations that should be taken into account for future scientific investigations in this field.