A 63-year-old man was found with confusion and right limb monoparesis. He was taken to the emergency center under suspicion of stroke. Head computed tomography and magnetic resonance (MR) imaging and MR angiography were immediately conducted, which revealed no abnormality, but diffusion-weighted imaging showed increased intensity areas in the splenium of the corpus callosum and the left posterior limb of the internal capsule with decreased apparent diffusion coefficient (ADC) in the same areas. Immediately after the head scan, blood sugar level was measured, which revealed hypoglycemia (23 mg/dl). He quickly became lucid after intravenous administration of 20 ml of 50% glucose solution, and the paresis disappeared. Follow-up brain MR imaging was conducted 3 days later, but no clearly abnormal findings were seen on T(2)-weighted, fluid-attenuated inversion recovery, diffusion-weighted, or ADC images. Reports of reversible high intensity area in the splenium of the corpus callosum on diffusion-weighted imaging due to transient hypoglycemia are rare. Hemiparesis is one of the manifestations of hypoglycemia, so verifying the blood sugar level is important. Since MR imaging can be conducted easily now, we may need to consider the imaging findings in the differential diagnosis of hypoglycemia.