The optimal treatment for aneurysmal bone cysts (ABCs) of the spine remains controversial. No treatment guidelines exist for the use of denosumab in aneurysmal bone cysts. In this report, we describe the results from a representative case and compare our experience with those of previously published reports.A 38-year-old male was referred for pain in the lower back and left leg. Radiographs and a needle biopsy specimen revealed a lumbar aneurysmal bone cyst, which was treated with denosumab chemotherapy. The pain in the lower back and left leg gradually improved, and at 16 weeks, the symptoms had resolved. Once a satisfactory local effect was achieved, denosumab therapy was discontinued. However, the erosive lesion subsequently expanded. After re-initiation of treatment, there was no subsequent evidence of recurrence.Single-therapy denosumab is an option for aneurysmal bone cysts. However, recurrences have been documented after denosumab termination, and the timing for cessation of denosumab is controversial.