OBJECTIVE: This study aims to share a very uncommon case of mastoidities with Actinomyces as the etiologic agent. CASE REPORT: This patient is 10 years old, previously asymptomatic, who began with a headache followed by retroauricular adenopathy, with subsequent purulent drainage in the right ear and hearing loss ipsilateral rapidly evolving. It is referred to our clinic after an absence of response to medical treatment with antibiotics. The Computerized Tomography was done which showed material with a soft tissue mass in the middle ear to the right, with the involvement of epitympanum and signs of erosion of the right lateral semicircular canal. Submitted timpanomastoidectomy right with perilymphatic fistula closure granulomatous tissue and sent for pathological examination, which showed the presence of bacterial colonies suggestive of Actinomyces, specific granulomas were not observed. After surgery, the patient was kept in hospital for 14 days for delivery of Crystalline Penicillin, and was discharged with a prescription for penicillin orally. CONCLUSION: The Actinomyces is a filamentous organism, gram positive and anaerobic, which normally inhabit the oral cavity, oropharynx and gastrointestinal tract. Although mastoidities caused by this organism is rare, should be considered in the differential diagnosis, especially in cases resistant to standard therapy.