Parasomnias are undesirable behaviors that arise from sleep but are not fully under voluntary control. Parasomnias are grouped broadly according to whether they arise from non-rapid eye movement (NREM) or rapid eye movement (REM) sleep. NREM parasomnias are disorders of arousal that occur along a continuum of behavioral, affective, and autonomic activation. REM-related parasomnias include REM sleep behavior disorder, sleep paralysis, and nightmare disorder. Parasomnias can often be managed successfully using behavioral and pharmacologic therapies.