Xanthogranulomatous osteomyelitis is a rare type of inflammatory process which is characterized by composition of immune cell aggregation on histological studies. Delayed-type hypersensitivity reaction of cell-mediated immunity may be implicated in its pathogenesis. Gross and radiological examination can mimic malignancy, and differentiation should be confirmed by histopathological evaluation. We describe the case of a 14-year-old Afghan boy presenting with pain in right shoulder and left leg with prior history of trauma. Fever, limitation in right shoulder range of motion, and tenderness in right shoulder and left thigh were detected following examination. Mild leukocytosis, elevated alkaline phosphatase, and increased erythrocyte sedimentation rate with negative C-reactive protein (CRP) were revealed. X-ray imaging showed mixed density, periosteal reaction, and cortical disruption. Computed tomography (CT) scan revealed lesions involving medulla and cortex, periosteal reaction with soft tissue component, and bone marrow infiltration in right humerus and left fibula. On magnetic resonance imaging (MRI), signal abnormalities in medulla, metaphysis, and diaphysis of the left fibula associated with cortical irregularity and diffuse soft tissue hypersignal areas were demonstrated. Finally, xanthogranulomatous osteomyelitis was confirmed by histological sample. The clinical manifestations and radiographic and laboratory findings of this rare condition are discussed.