This is a case report of hyperbaric oxygen therapy (HBO2T) for ischemic stroke. HBO2T should be the potential or additional treatment (with thrombolytic therapy) for ischemic stroke according to the preclinical and clinical studies. Hereby, we present a 56-year-old Chinese man with vascular risk factors. He had an acute ischemic stroke on the left corona radiata, with right hemiparesis and dysarthria resulting from atherosclerosis. The patient could not get thrombolytic treatment because the time to ER was in excess of five hours. He experienced great improvement after the general course of HBO2T; this was evaluated with standard rating scales for stroke research and cerebral perfusion images, including brain-computed tomography perfusion (CTP) and single-photon emission computed tomography (SPECT). Although few clinical trials showed a negative result, we suggest that further trials on HBO2T are still needed. Meanwhile, we emphasize the importance of HBO2T protocol and the selection of a suitable patient, which may influence the outcome.