Arterial dissection is a rare but serious cause of acute childhood stroke. Here, we present the case of a 15-year-old adolescent boy, an art school student, who suddenly experienced left hemi-paralysis after performing repeated backward somersaults, diagnosed as right-sided middle cerebral artery (MCA) hyperacute infarct due to isolated MCA dissection. Middle cerebral artery dissection in childhood is rare, as in our patient; however, pediatricians and emergency physicians should take MCA dissection into consideration in the differential diagnosis when hyperdense MCA sign is detected from unenhanced cranial computed tomography (CT) of childhood and/or adolescent stroke, with a special history such as backward somersault as in this case. Besides, unenhanced cranial CT and further imaging studies, including CT angiography and magnetic resonance imaging, provide a crucial role in early diagnosis to design proper treatment of acute childhood stroke in the ED.