Kleine–Levin syndrome (KLS) also called sleeping beauty syndrome, is a rare sleep disorder with onset in early adolescence. Common symptoms are episodes of hyper somnolence, behavioral and cognitive disturbances (including specific feelings of derealization), hyperphagia and hypersexuality. The cause is not known and neither there are any definitive management guidelines. It remains a diagnosis of exclusion after ruling out other psychiatric and neurological disorders. Our case, a 15 year old boy with duration of illness of 3 years, episodic presented with hypersomnia, increased appetite, irritability, hyper sexuality and behavior abnormality mainly fearfulness and suspiciousness. Patient responded well to lithium therapy. The priority of this report is to add the existing clinical knowledge of psychiatrists, neurologists and physicians.