Intensive care unit acquired weakness (ICUAW) is a neuromuscular disorder of skeletal and respiratory muscles that occurs in critically ill patients in intensive care units (ICU) and occurs due to the critical illness itself or its treatment, and in the absence of a primary neuromuscular disorder. ICUAW is a clinical diagnosis that includes three separate syndromes which are critical illness myopathy (CIM), critical illness polyneuropathy (CIP) and their overlap syndrome critical illness neuromyopathy (CINM). The clinical presentation of this syndrome includes generalized and symmetrical muscle weakness that affects limbs and respiratory muscles which leads to difficulty in weaning from mechanical ventilation, while facial and ocular muscles are spared. The diagnosis of ICUAW includes clinical diagnosis through volitional functional testing, of which the MRC sum score is the gold standard. Since distinguishing between CIM and CIP is impossible based on clinical tests, electrophysiological testing and histological analysis of muscles and nerves are needed for their diagnosis. The incidence of the syndrome is not precisely determined, and it ranges from 9% to 86%. Although many possible mechanisms of the syndrome have been proposed, its pathophysiology has not been fully clarified yet. Risk factors have not been researched enough and there are still disagreements and conflicting results across different studies. Due to the incompletely explained pathophysiology and inconsistent results across studies of risk factors, methods of prevention and treatment are mostly unsuccessful. This syndrome causes an increase in mortality, prolongs the time spent on mechanical ventilation and the length of stay in the ICU and hospital, increases the cost of treatment and causes swallowing disorders. After discharge from the hospital, many patients are left with reduced physical functionality, which greatly reduces the quality of life and prolongs the rehabilitation. Considering these severe consequences, it is important to carry out further extensive research in order to clarify the pathophysiology of the syndrome and thus develop adequate methods of prevention and treatment.