Separation anxiety disorder (SAD) is characterized by excessive anxiety about being apart from the individuals to whom a child is most attached. We noticed a case of a 13 year old boy's SAD with symptoms of nausea/vomiting, stomachache, school refusal, and severe weight loss. His mother was overanxious and overdependent but her dependency was frustrated due to family problem. We investigated this case from a point of developmental aspect and family dynamics and tried to attempt therapeutic approach.