DNA methylation is an epigenetic mechanism in mammals where a methyl group is transferred to the C5 position of cytosine, forming 5-methylcytosine. This process regulates gene expression by recruiting proteins involved in gene repression or inhibiting transcription factor binding. During development, the pattern of DNA methylation changes through de novo methylation and demethylation, leading to a stable and unique pattern in differentiated cells. Postmitotic neurons still express DNA methyltransferases and components involved in DNA demethylation, and neuronal activity can modulate their patterns in response to physiological and environmental stimuli. Proper DNA methylation is crucial for normal cognitive function, and alterations can lead to mental impairments. The investigation of DNA methylation provides insights into epigenetic gene regulation in the central nervous system and potential therapeutic targets for neuropsychiatric disorders. The chapter reviews the basic functions of DNA methylation, its role in neural development, and its involvement in neurological and psychiatric disorders.DNA methylation is an epigenetic mechanism in mammals where a methyl group is transferred to the C5 position of cytosine, forming 5-methylcytosine. This process regulates gene expression by recruiting proteins involved in gene repression or inhibiting transcription factor binding. During development, the pattern of DNA methylation changes through de novo methylation and demethylation, leading to a stable and unique pattern in differentiated cells. Postmitotic neurons still express DNA methyltransferases and components involved in DNA demethylation, and neuronal activity can modulate their patterns in response to physiological and environmental stimuli. Proper DNA methylation is crucial for normal cognitive function, and alterations can lead to mental impairments. The investigation of DNA methylation provides insights into epigenetic gene regulation in the central nervous system and potential therapeutic targets for neuropsychiatric disorders. The chapter reviews the basic functions of DNA methylation, its role in neural development, and its involvement in neurological and psychiatric disorders.