The aim of this case report to investigate mania due to a left temporal lobe neoplasm previously diagnosed with Asperger Syndrome. Left hemispheres brain tumors involving the atrophic and cystic lesion in the cortex which could be the reason of mania have been rarely described in the literature. In such cases, early neurologic signs might be confounded and hard to make the differential diagnosis from some of the psychiatric disorder. Mania secondary to left brain neoplasm is an extremely rare phenomenon which has not been previously reported in the literature. Brain magnetic resonance imaging (MRI), baseline electroencephalogram (EEG), and neuropsychiatric evaluations were used to examine the relationship between the patient’s brain lesion and behavioral disturbances. A patient diagnosed as Asperger syndrome in a childhood period developed mania during the course of following period. Some of the psychiatric symptoms related with social cognition impairment, inability to maintain social relationships and recognizing social clues were the main problem of the patient. He has experienced multiple manic and depressive despite the use of antipsychotic, anti-depressive and mood stabilizers drugs. As a result of further investigation test results, cystic and atrophic tumor in temporal lobe hippocampal region and choroid plexus papilloma were observed. Those of the symptoms related with mood and behavioral disturbance, social cognition impairment and occupational disability could be well explained by the organic brain lesion. It was also reported some of the organic problems related with perception and motor coordination determined by the further neuropsychological evaluation. EEG tests results were in a normal range Organic lesion in temporal lobe might be a trigger of the emotional and behavioral disturbance. This case suggests that clinicians should be aware of unexplained cases presented with manic and depressive symptoms. In conclusion; right temporal lobe astrocytoma associated with bipolar disorder has been described in literature. It could be the first case report associated with left temporal hypothalamic tumor, which will cause bipolar disorders.