Given the high prevalence of social impairments in children with Attention Deficit Hyperactivity Disorder (ADHD; Nijmeijer et al., 2008), it is important to understand how ADHD symptomatology relates to children’s social interactions. The three major symptoms of ADHD include inattention, hyperactivity, and impulsivity. As such, children who are high on ADHD symptomatology may have difficulty controlling their negative emotional responses and motor behaviors, which may result in aggressive behaviors towards peers. We hypothesize that children with higher ADHD symptomatology will show more aggression towards unfamiliar peers in the lab. Participants (N = 291) were 4-year-olds recruited from an ongoing longitudinal study investigating the impact of infant temperament on development. ADHD symptoms were assessed using parent report on the ADHD scale of the Child Behavior Checklist. Aggression was observed in the lab during an unstructured free play task with an unfamiliar peer. The regression results indicated that ADHD symptomatology was positively related to aggression toward unfamiliar peers (𝛽 = 0.177, p = 0.011), even after accounting for gender differences with boys showing more aggression than girls (𝛽 = 0.238, p = 0.001). Our findings suggest that children with higher ADHD symptomatology show more aggression towards peers in the lab. This may be a reasonable explanation as to why children diagnosed with ADHD also encounter social problems at school. A viable strategy for prevent social impairments in children with high ADHD symptomology may be helping them learn how to control aggressive behaviors towards peers.