Systemic capillary leak syndrome (SCLS) is characterized by intermittent attacks of leakage of intravascular fluids into the extravascular space. Hypovolemia, hemoconcentration, weakness, edema, and visceral congestion are resulting manifestations of SCLS. Most patients with SCLS have clear mentation during attacks, and encephalopathy is not a known manifestation of the syndrome. We report a patient with acute idiopathic capillary leak syndrome manifested in an acute encephalopathy. The possibility of SCLS should be considered in patients who have an encephalopathy and hemoconcentration.