Cerebrotendinous xanthomatosis (CTX), a rare familial lipid metabolic disease inherited via an autosomal recessive trait, is caused by mutations of the sterol 27-hydroxylase gene. Psychiatric disorders may occur in patients with CTX. In Taiwan, Chang et al presented patients with CTX. However, there has not been a case presented about CTX with psychiatric disorders in Taiwan. We present three siblings in one family with CTX combined with moderate mental retardation. One of the siblings had long-term depressed mood, irritability, poor appetite, insomnia, fatigability, and pessimistic thinking and was diagnosed as dysthymic disorder. After 2.5 years of antidepressant treatment at our outpatient clinic, the depressive symptoms of the dysthymic sibling improved greatly. However, the results of the IQ tests of the three siblings did not change after effective treatments for physical manifestations of CTX. In addition, the authors reviewed the literature of CTX combined with psychiatric disorders.