Symptomatic os trigonum is a rare condition, well described in adults, that causes chronic ankle pain. To date there are no reported cases of successfully managed symptomatic os trigonum in the children population. We retrospectively reviewed four paediatric patients (11-17 years of age) successfully operated for a symptomatic os trigonum using an open excision through a posteromedial approach. One case was bilateral. Postoperative pain relief was obtained in all cases. All of the patients were able to return to unrestricted physical activities after three months. The average follow-up was 12 months. Symptomatic os trigonum may be held responsible for chronic ankle pain in children and adolescents as well as in adults. The surgical treatment is effective in children.