This article presents the case of an infant who underwent an orthotopic liver transplant and then developed hepatic artery thrombosis that was detected on routine post-operative right upper quadrant ultrasound. Alteplase (TPA) failed to open the artery, so the child received systemic heparin and hyperbaric oxygen (HBO) therapy. After six HBO treatments, the hepatic artery had recanalized and his liver function tests had returned to normal or near normal. There were no complications to the HBO therapy, and 1 yr after the transplant, the child's liver is functioning well. The present study discusses the beneficial effects of HBO therapy and the proposed mechanisms for its favorable results. In our patient, systemic heparin and HBO therapy prevented liver failure and need for retransplantation.