Rationale: Primary bone lymphoma (PBL) is a rare malignant entity. There is a better survival of PBL than any other malignant bone tumors and extranodal lymphomas. Patient concerns: We report a rare case of PBL involving radius and tibia. The patient was a 14-year-old girl with left forearm pain and swelling after trauma. Six months later after the last chemotherapy and radiotherapy, pain and swelling of left knee was presented. Diagnoses: Radiological imaging revealed a lytic destruction, periosteal reaction, and pathological fracture of radius and tibia with soft tissue mass. Surgical biopsy was performed, and the result of histopathological diagnosis was diffused large B-cell lymphoma (stage IV, group A). Intervention: Chemotherapy combined with radiotherapy was applied before curation. Lessons: Due to its uncommon presentation, PBL should be taken into consideration if differential diagnosis from other bone tumors is necessary in clinic.