Actinomycosis is a relatively uncommon bacterial disease of childhood, especially when presenting as deep-seated infections. Only 10% of affected patients are younger than 18 years of age. In children, cervical actinomycosis is the most common form of clinical presentation, and among the abdominopelvic form, renal abscesses are rare. We describe an uncommon and severe case of a five-year-old Costa Rican girl with thoracic and renal actinomycosis who required a complete nephrectomy.