Depression is one of the main psychiatric comorbidity reported in individuals with autism spectrum disorder (ASD). However, some cases of bipolar disorder accompanying ASD have been reported. In the past, there was a tendency to attribute all psychiatric problems in autistic children and adults to autism itself. Nowadays, there is not only an increase in the number of studies on other medical conditions especially neurological conditions in ASD but also there is an increasing effort in defining the comorbide psychiatric disorders. Comorbid psychiatric conditions can make disease management difficult in cases of autism. The precise and reliable diagnosis of psychiatric disorders accompanying children and adolescents with autism is of great importance. More specific treatment options are possible when problematic behaviors are accepted only as a manifestation of comorbid psychiatric disorder from isolated behavior. In this case report, we aimed to present the diagnosis and management of an adolescent autism diagnosed patient and comorbid bipolar disorder.