Moyamoya disease (MMD) is a rare blood vessel disorder occurring  in people from Japan & other Asian countries, but people in other countries also have been diagnosed with MMD. Impaired neuropsychological functioning is a common sequelae of MMD in children as well as adults. We report a first Indian case (male, diagnosed as MMD at 8 years) was referred for neuropsychological evaluation (NPE) at 12 year, revealed impaired intellectual functioning with moderate retardation on social adaptive functioning. After 2 years of follow up, post psychosocial intervention, the patient showed remarkably upword trend in his social adaptive functioning, with shift in his intellectual functioning by 21 I.Q.points thereby brining him to mild category of mental retardation. Therefore, this rare case shows improved neuropsychological functioning, highlighting importance of interplay between nature and nurture roles. Hence, NPE is sensitive in comparing & drawing inferences for  neuropsychological rehabilitation & pharmacological management for such patients.