We report a severe and not previously reported toxicity after short-interval retreatment with stereotactic body radiotherapy (SBRT) in a pediatric patient with neuroblastoma. This patient experienced Grade III radiation myositis after treatment with conventional radiation therapy followed by high-dose SBRT for persistent disease a short interval after the initial radiotherapy course. While SBRT shows outstanding rates of local control in adult disease, data in pediatric cancers are extremely limited. In this report, we discuss the rationale of SBRT in this patient's multimodality neuroblastoma treatment, management of the toxicity, and future perspectives on the use of SBRT in pediatric cancer.