Mixed and rapid cycling types of bipolar disorder are more frequent in adolescent patients than the adult ones. It usually causes a decline in academic success, social and family functionality and increased suicide rates, legal issues. Therefore, it should be treated on time with the proper effective way. However, there is a limited data about the treatment of bipolar disorder in childhood and adolescent ages. There are very few studies published in last 10 years, which are credible and forward. The efficiency of lithium and other mood stabilizers, either monotherapy or in combined treatment, have been supported with studies consistently. Studies about the pharmacologic treatment of bipolar disorder in adolescents usually focused on acute mania episodes and subjects like depressive episode treatment, maintenance treatments, and comorbid diseases are relatively less studied. Besides, more studies are needed about the reliability, efficiency, tolerability, neurobiological effects on sick or under-risk child of medial ages. This female adolescent presented initially at 15 years old with anxiety symptoms manifest as school refusal, social avoidance, and panic, as well as escalating verbal and physical aggression. A. was placed on şuoxetine 25 mg /day at age of 15, and following a school reintegration plan, she was able to have one year of more stable function. She presented again at the age of 17, in our clinic, uncontrollable physical aggression, excessive talking, insomnia and spending a lot of money. She was started on valproate and quetiapine to modulate her mood and explosive outbursts. She was given a DSM-IV-R diagnosis of bipolar disorder type I. In our study, which we present as a case report, we discussed the clinical aspects, differential diagnosis, current treatment approaches of bipolar disorder in a female adolescent inpatient diagnosed as bipolar disorder (manic episode) in the light of the literature. The conception that bipolar disorder or manic–depressive illness could occur in childhood and adolescence has only recently been accepted, and some authors even suggest that it may be under-diagnosed, especially in adolescents. Some of the difficulties in diagnosing bipolar disorder in adolescents are atypical presentation, developmental inşuences, and comorbidity, especially with externalizing disorders. Clinicians need to be aware of the various presentations of adolescent-onset bipolar disorder.