Posterior ankle impingement is a cause of posterior ankle pain common in those who perform frequent plantarflexion activities. Three young patients presented with posterior ankle pain which was initially attributed to peroneal tendon subluxation. However, detailed physical exam and imaging confirmed the diagnosis of posterior ankle impingement as the actual cause of pain. The peroneal tendon subluxation was not causal but an unrelated co-incidental finding. After failed prolonged conservative management (rest, immobilization and physical therapy), the patients underwent posterior ankle arthroscopic debridement for the impingement resulting in return to prior sporting activity without limitation and no recurrence of pain at 19 months follow-up. Posterior ankle impingement diagnosis could be masked by co-incidental asymptomatic peroneal tendon subluxation in pediatric patients.