Background; The aim of this work was to investigate the choroidal morphologic changes of Vogt–Koyanagi–Harada (VKH) disease in vivo using high-penetration optical coherence tomography (HP-OCT) with a long-wavelength light source (1,060 nm). Methods; Six patients with VKH disease were included in this study: 12 eyes of six patients with treatment-naive acute VKH in the first 6–12 months after diagnosis. HP-OCT was used to observe the deep choroid and sclera. The choroidal thickness was measured for 6-12 months in eyes with acute disease. Results; In 12 eyes with acute VKH disease, the baseline choroidal thickness was significantly (p<0.0001) greater than in controls. After treatment, the choroidal thickness decreased over time. However, the choroidal thickness increased markedly again in four eyes with recurrent disease. The mean thickness at 12 months was significantly less than the normal value (p < 0.0001). Conclusions; Significant choroidal thickness changes underlie VKH disease, which progress over time. Objective measurement of the choroidal thickness using HP-OCT may be useful for longitudinal evaluation of VKH activity.