Stiff person syndrome is a neuroimmunological disorder characterized by progressive muscular rigidity and spasms that affect axial/limb muscles, resulting in severe pain and functional limitations. When refractory to conservative treatments, intrathecal baclofen is a viable option to treat the increased tone. Intrathecal baclofen has been shown to accelerate underlying neuromuscular scoliosis in the pediatric population with cerebral palsy. This adverse effect has never been reported in adults with stiff person syndrome. We report a case of an adult with stiff person syndrome and underlying scoliosis who experienced accelerated progression of scoliosis after initiation of intrathecal baclofen, subsequently requiring neurosurgical intervention.