We present a case of an 8 year-old girl with a large aneurysmal bone cyst (ABC) of the 4th lumbar vertebra that involved the adjacent posterior element and which was treated by an en bloc excision. An aneurysmal bone cyst is an uncommon lesion. Among lesions that involve the extremities, standard treatment with curettage and a bone graft or other alternatives, such as embolization and radiation therapy, may be sufficient; but those that involve the spinal column require special consideration because of its anatomical and biomechanical complexity. We removed a large aneurysmal bone cyst from the posterior element of the lumbar spine with an en bloc excision without fusion or instrumentation and the clinical result was satisfactory. At the 1-year follow-up, there was no evidence of clinical recurrence or radiological instability. We describe a case of a large aneurysmal bone cyst of a lumbar vertebra of a child and present a review of the pertinent literature.