Aneurysmal bone cysts (ABCs) are benign, highly vascular osseous lesions characterized by cystic, blood-filled spaces surrounded by thin perimeters of expanded bone. Children and young adults are most often affected by spinal ABCs; more than 75% of patients are younger than 20 years old at presentation. Although ABCs have been documented in all areas of the axial and appendicular skeleton, ABCs of the spine present unique challenges due to the risk of vertebral destabilization, pathological fracture and vertebral body (VB) collapse, and neurological compromise. The authors describe the case of an 8-year-old child who presented with low-back pain and was subsequently found to have a lumbar ABC causing vertebra plana of the L-3 VB. They also review the literature on ABCs of the spine. This case highlights the importance of considering an ABC in the differential diagnosis when vertebra plana is seen in pediatric patients.