Subcutaneous emphysema is an abnormal appearance of gas in the subcutaneous tissue. Because subcutaneous emphysema may be easily confused with other facial swelling causes and lead to severe complications and life-threatening situations, dentists should make an early differential diagnosis and prevent the complications actively. Subcutaneous emphysema is an uncommon complication in dental treatments but could occur in teeth extraction using air-driven handpieces and posterior mandible teeth extraction. In this case report, we describe a case of subcutaneous emphysema caused by the failure of the high-speed handpiece during the removal of the third molar of the lower jaw. We present this report and review related literature because the surgical procedures, instruments, and treatment location, in this case, are common factors associated with the complication of subcutaneous emphysema in dental treatment.