This study examined the relation between self-representation and brain development in infants and young children. Self-representation was assessed by mirror recognition, personal pronoun use, and pretend play. Structural brain images were obtained from magnetic resonance imaging (MRI). Brain development was assessed by a quantitative measure of maturation of the temporo-parietal junction, temporal pole, medial frontal cortex, and occipital cortex. Fifteen children (15 to 30 months of age; 3 girls) without MRI abnormalities were assessed. Only maturation of the left temporo-parietal junction was related to self-representation after controlling for age. These findings provide some evidence that brain maturation is related to the emergence of a representation of self in the human child. (Contains 2 tables.)