Dystonia is a movement disorder that has various treatment options. For primary dystonia, stereotactic procedures such as deep brain stimulation (DBS) have demonstrated favorable outcomes. For secondary dystonia, however, the treatment outcomes remain inconclusive, and the heterogeneous etiological background is considered to contribute to the poor outcomes of the disease. Here, we report a rare pediatric case of post-stroke focal dystonia treated with conventional radiofrequency ventro-oral (Vo) thalamotomy. The patient was an 11-year-old girl with secondary focal dystonia in her right hand. The dystonia was considered to result from a stroke lesion in the putamen due to vasculitis following varicella-zoster virus infection. We hypothesized that the infarction of the putamen resulted in hyperactivity in the thalamus, and, thus, performed a radiofrequency Vo thalamotomy. Markedly decreased muscle tone in her right hand was noted immediately after surgery. However, the improvement was temporary, as her symptoms returned to baseline level by the 6-month follow-up. Although the observed improvement was temporary in this case, our findings may elucidate the possible mechanisms of secondary focal dystonia. Further studies are needed to establish an effective surgical treatment for secondary focal dystonia.