Introduction . To describe a rare case of solitary bone cyst in the vertebral body of the lumbar vertebra in an adult patient. The solitary bone cyst is defined as a cystic lesion with liquid content. Few cases have been described in the vertebral location without preference for the posterior arch or vertebral body. Most have been treated with resection, curettage, and/or grafting. No case described to date has been treated with polymethylmetacrylate (PMMA) injection in the vertebral location. Case Presentation . A 50‐year‐old male patient was consulted for lumbar pain with no traumatic history and no neurologic deficit. The radiological study showed lumbar arthrodesis with L2‐L4 instrumentation due to an L3 fracture twenty years earlier. Computed tomography (CT) scan showed a lytic lesion occupying practically the entire vertebral body of L5, with incomplete septum and sclerotic edge, without cortical rupture. The previous steel instrumentation was removed, to avoid the presence of artifacts when performing the magnetic resonance (MR), and a biopsy of L5 vertebra was performed via transpedicular in the same act. The MR study findings and biopsy were compatible with the simple bone cyst. Finally, a new intervention was performed by filling the lesion with PMMA. Follow‐up at 5 years was satisfactory without lumbar pain as well as the radiological study and with a return to previous activity. Conclusions . The spinal location of the simple bone cyst is extremely infrequent. Its diagnosis excludes other lesions and is made by imaging studies and biopsy. Treatment can be performed by excision, curettage, or filling with graft or as in this case, with PMMA.