Hereditary hemorrhagic telangiectasia is a rare autosomal dorminant disease that features abnormal and fragile vascular dilations of terminal vessels in skin and mucous membranes, as well as arteriovenous malformations of internal organs, particularly lungs, brain, and liver. Often patients have not been diagnosed with HHT for a long time, and undiagnosed HHT patients unnecessarily develop serious complications such as severe life-threatening hemorrhage, stroke or brain abscess. Therefore, early detection and appropriate screening is very important. Early detection of HHT allows the appropriate screening for the presence of silent disease such as AVMs in the lungs, liver, or brain, and preventive treatment in the patient and their affected family members. Dentists should be familiar with HHT because the telangiectases on skin and oral mucosa are often the most dramatic and most easily identified component of HHT. Recently, we experienced a case of HHT. We present the case with a review of the literature.