Tolosa-Hunt syndrome (THS) is a rare disorder, especially in the pediatric population, characterized by unilateral painful ophthalmoplegia with a relapsing-remitting course. Because the diagnosis of THS is based on the exclusion of other causes of painful ophthalmoplegia, attention should be paid to possible alternative diagnoses. Thallium-201 chloride ((201)Tl) scintigraphy has been used to evaluate tissue histology in clinical oncology with a marker, the retention index (RI). A higher value indicates histological malignancy. Although its utility in pediatric THS has not been discussed, we suggest that (201)Tl scintigraphy may be informative as a marker in the diagnosis. We present an 11-year-old boy with THS who was evaluated with (201)Tl scintigraphy before treatment with corticosteroids, when he had headache, photophobia, and diplopia. The RI of (201)Tl indicated that the lesion would be benign. Although his clinical symptoms did not fulfill the THS criteria completely, his eye symptoms disappeared 2 weeks after corticosteroid treatment, which was not within the 72 h as in the diagnostic criteria of THS. He has been symptom-free for more than 2 years with only an initial 4-week corticosteroid therapy. This report not only shows the potential of (201)Tl scintigraphy to contribute to the correct diagnosis of pediatric THS but also suggests the possibility that the diagnosis of THS could be supported uniquely even in a pediatric THS-suspicious patient who did not fulfill the current THS criteria completely. In conclusion, we suggest that (201)Tl scintigraphy may be useful for making the diagnosis of THS, especially in pediatric patients.