The European League Against Rheumatism and the American College of Rheumatology have stated that the halo sign on vascular ultrasonography (v-US) is relevant in diagnosing giant cell arteritis (GCA) and is equivalent to temporal artery biopsy. However, there are only a few reports about transitions in v-US findings after glucocorticoid (GC) therapy. We report the transitions in the v-US findings in a case of GCA after GC therapy. The patient had rapidly progressive symptoms, and there were concerns about blindness. After GC therapy, we first observed improvement in headache and visual impairment symptoms within 1 week, followed by rapid improvement in laboratory findings within 2 weeks. Subsequently, there were improvements in v-US findings after more than 2 months. In conclusion, these findings showed a dissociation between improvements in clinical symptoms and v-US findings of the temporal artery. Additionally, this case suggests that regular examination of v-US findings is useful in evaluating GCA with evident vascular wall thickness before GC therapy.© Japan College of Rheumatology 2023. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: firstname.lastname@example.org.