Mobilization is often used by physiotherapists for managing critically ill patients with the aim of treatment including improving respiratory function, level of consciousness, functional ability, and psychological well being, and reducing the adverse effects of immobility. In addition, mobilization may decrease the duration of mechanical ventilation and length of ICU or hospital stay. This article provides ICU practitioners with comprehensive guidelines that can be used to assess the safety of mobilizing critically ill patients. The main safety factors that should be addressed include intrinsic factors related to the patient (eg, medical background, cardiovascular and respiratory reserve, and hematological considerations) and factors extrinsic to the patient (eg, patient attachments, environment, and staffing).