A 23-year-old woman presented with disturbance of consciousness and seizure. Her blood pressure was remarkably high, and brain magnetic resonance imaging (MRI) showed high-intensity T2 signals in the bilateral basal ganglia, corpus callosum, cerebral white matter, and cortex. With the administration of angiotensin II receptor blocker, the symptoms and MRI findings improved, along with normalization of blood pressure, and a diagnosis of posterior reversible leukoencephalopathy syndrome (PRES) was made. Plasma renin activity was high, and the right kidney was severely atrophic. Results from renal and adrenal vein sampling revealed renal vascular hypertension derived from the right renal artery stenosis. The right kidney was then removed by laparoscopic nephrectomy. Pathological examination of the kidney confirmed the diagnosis of fibromuscular dysplasia (FMD). In juvenile-onset encephalitis/encephalopathy, PRES due to FMD should be included in the differential diagnosis.