Mitochondria are intracellular organelles crucial to the production cellular energy. Mitochondrial disease results from a malfunction in this biochemical cascade. These disorders can affect any organ system, producing diverse signs and symptoms, including psychiatric ones. Several authors argue that mitochondrial dysfunction is related to the pathophysiology of bipolar disorder and schizophrenia. Also, the authors retrieved 19 case reports that describe patients with mitochondrial diseases and psychiatric disorders. Most of these patients have psychiatric presentations that preceded the diagnosis of mitochondrial disease. The most common physical findings are fatigue, muscle weakness with or without atrophy, and hearing loss.