Previous observational studies conducted in highly structured, analog situations indicate that children with Attention-Deficit/Hyperactivity Disorder (ADHD) mismanage their relationships with same-age peers and friends. Such structured situations may not, however, fully represent the true nature of children’s play, which is typically characterized by free choice, intrinsic motivation, and spontaneity. The unique objective of the current observational study was to describe how 87 children with ADHD and 46 comparison (76% boys) aged 7–13 years behave when interacting with their real-life dyadic friends during an unstructured, free-play situation. Results indicate that dyads comprising one referred child with ADHD and an invited friend (“ADHD dyads”) engaged in less cooperative play, displayed less companionship, and showed less sensitivity to friends than comparison dyads. ADHD dyads also engaged in more conflict and exhibited significantly more negative affect than comparison dyads. These findings complement and extend, possibly with somewhat enhanced ecological validity, results obtained in previous studies on the friendships of children with ADHD featuring closed-field observations and questionnaire methodology.