Actinomycosis is a chronic granulomatous disease caused by Gram-positive anaerobic bacteria of the genus Actinomyces. Pulmonary actinomycosis is a rare infection in children, and its extension into the chest wall is infrequently reported. We report a case of pulmonary actinomycosis in a 14-year-old girl of Mapuche descent who presented with chronic respiratory symptoms and multiple discharging skin sinuses on her right lower chest wall. The diagnosis was made by skin biopsy, which showed sulfur granules with actinomyces colonies. She was successfully treated with intravenous ceftriaxone and penicillin G for 6 weeks, followed by oral amoxicillin for 6 months.