We report a pediatric case of intrathecal baclofen therapy for severe spasticity following traumatic brain injury. A 14-year-old boy suffered from traumatic brain injury by traffic accident in 2005. Subsequently, he experienced tetraparesis and severe spasticity with spontaneous spasms. He underwent baclofen screening test, and his spasticity was improved. Thereafter intrathecal baclofen therapy was performed. Following baclofen pump implantation, Ashworth Score decreased from 4.0 points to 3.0 in lower limbs, and from 3.0 to 1.5 in upper limbs. His muscle tone was reduced and occurrence of spontaneous spasms stopped. Intrathecal baclofen therapy was observed to be an effective treatment for severe spasticity in childhood. Since children receiving the therapy demonstrated longer survival period than adults, long-term follow-up of this therapy is warranted.