A 40-year-old male with osteogenesis imperfecta (OI) was admitted to the hospital with an acute right monoparesis. Diffusion-weighted MRI showed infarction in the territory of the left anterior cerebral artery (ACA) and in the left posterior cerebral artery (PCA). In his vascular imaging, occlusion of the left vertebral artery (VA) starting from V2 segment was consistent with dissection and pseudoaneurysm in the right ACA. We presented this case because of the presence of spontaneous and simultaneous occurrence of both intracranial and extracranial arterial dissections in OI.