We report here on the MR findings of the first Korean case of hand-foot-mouth disease (HFMD) complicated by acute enterovirus 71 (EV 71) encephalitis in a 33-month old girl. Conventional MR images of the patient showed the increased signal intensity (SI) on a T2-weighted image (WI) at the posterior aspect of the medulla, the pontine tegmen, the bilateral dentate nuclei of the cerebellum and the midbrain. There was no evidence of abnormal SI or contrast enhancement at the same areas of the brain on the pre- and post-contrast T1-WI. The diffusion weighted images (DWI) also revealed the bilateral symmetrical strong high SI at the posterior aspect of the medulla and pontine tegmen and there was low SI at the same areas on the apparent diffusion coefficient (ADC) map. DWI in addition to the conventional MR imaging may be helpful for the early detection of acute EV 71 encephalitis in a patient with HFMD.