Mitochondrial respiratory chain disorders are a group of genetically and clinically heterogeneous disorders caused by the biochemical complexity of mitochondrial respiration and the fact that two genomes, one mitochondrial and one nuclear, encode the components of the respiratory chain. These disorders can manifest at birth or present later in life. They result, at least in part, in defective production of ATP. Typically, mitochondrial disorders affect tissues with high energetic demands such as skeletal muscle, cardiac muscle, and the central nervous system. Neurological dysfunction is the most frequent clinical presentation of these disorders. The central nervous system is highly dependent on oxidative metabolism, and particular mitochondrial disorders are accompanied by focal brain necrosis (Leigh disease), dementia, or static encephalopathy. Furthermore, many children with mitochondrial encephalomyopathies present with more subtle and indolent signs including focal cognitive deficits of memory, perception, and language. Some subjects with mitochondrial disorders may also exhibit nonverbal cognitive impairment, compromised visuospatial abilities, and short-term memory deficits associated with working memory that likely reflect defects in synaptic plasticity. Psychiatric features are found within the clinical spectrum of mitochondrial syndromes. It is increasingly recognized that mitochondrial dysfunction may be associated with neuropsychiatric abnormalities such as dementia, major depression, and bipolar disorder. Furthermore, several lines of evidence suggest that there is involvement of mitochondrial dysfunction in schizophrenia, including documented alterations in brain energy metabolism, electron transport chain activity, and expression of genes involved in mitochondrial function. The purpose of this review article is to summarize the psychiatric features observed in mitochondrial cytopathies and discuss possible mechanisms of dysfunctional cellular energy metabolism that underlie the pathophysiology of major subsets of psychiatric disorders.