To acquire age-appropriate social skills, certain parts of the brain need to develop normally. Children with ADHD may experience social difficulties and experience what is called a social cognition deficit. This chapter outlines social clumsiness in ADHD. It discusses social cognition as a function of the brain, specific social competence deficits (social blindness, egocentricity, lack of appropriate inhibition, insatiability, insensitivity to style and convention, lack of responsiveness, over-talkativeness, difficulties reading facial expression, aggressive tendencies, lack of judgment, poor understanding of group dynamics, misinterpretation of feedback, poor social prediction, poor social memory, lack of awareness of image, poor behaviour-modification strategies), management of social clumsiness, and autism spectrum disorder.