Solitary plasmacytoma of the bone (SPB) is a rare plasma cell neoplasm representing only about 5% of plasma cell neoplasia. It usually presents as a lytic lesion mainly localized within the axial skeleton. SPB is exceedingly rare in young individuals, and only few cases have been reported so far in patients younger than 20 years of age. In view of rarity of disease, definitive treatment guidelines have not been established. We hereby report a case of SPB involving of lumbar vertebra (L5) in a 12-year-old boy. He was initially treated with antilymphoma therapy and curative radiotherapy considering as primary bone lymphoma. However, he had local recurrence with paraparesis after 9 months which was diagnosed as solitary bone plasmacytoma for which he was treated with decompressive laminectomy and chemotherapy (bortezomib, lenalidomide, and dexamethasone). The purpose of this article is to report a rare case of SPB in a pediatric patient and to review the available literature and treatment options. SPB should be considered in the differential diagnosis of osteolytic bone lesions even in young patients.