In the extremity surgery, pneumatic tourniquet and povidone-iodine solution are commonly used to provide an aseptic, bloodless field, and their complication rate has remained low. However, chemical burn under tourniquet has been rarely reported. Patients sustained burn injuries over the dependent, weight-bearing regions such as posterior neck, back, buttocks and posterior thighs. This rare adverse complication occurred in a 22-year-old man who underwent modified Brostrom operation with arthroscopic os trigonum excision. 10% povidone-iodine was used as topical antiseptic, and full thickness burn occurred underneath the area of tourniquet application. Main causes of povidone-iodine related chemical burn are considered maceration, irritation of the skin, long term use of the tourniquet and pressure. To reduce the complications like chemical burn, awareness of the risk and the possible pathogenesis as well as the preventive measures is important in surgical practice.