Brucellosis is uncommon in children. In Thailand, there have been only seven adult cases reported, all with Brucella melitensis. We describe here the first reported pediatric case of brucellosis in Thailand. A 12-year old boy presented with prolonged fever for one month, pancytopenia, pneumonia and peritonitis. The blood culture grew out Brucella melitensis. He responded well to combination therapy consisting of doxycycline and gentamicin. He recovered fully without relapse during the 6 month follow-up.