The use of hyperbaric oxygen therapy (HBOT) is an accepted method of supporting wound healing in human medicine. Yet, because of the risk of complications associated with HOBT, a safer modification of the therapy, known as L-HOBT (lower pressure and lower oxygen concentration), is increasingly used nowadays. Therefore, due to the lack of literature reports regarding the clinical use of L-HBOT in animals, the authors decided to present the results of L-HBOT supportive treatment of postoperative wounds after hemimastectomy compared to classic treatment. The study group included 12 bitches divided into two groups: group A (assisted L-HBOT) and group B (classic treatment). In addition to conventional treatment, the supportive therapy included 1.5 hours of hyperbaric chamber therapy for 5 consecutive days, starting 24 hours after surgery (1500hPa pressure and 26% oxygen concentration in the chamber). The patients were followed and evaluated throughout the course of the treatment by two independent doctors. The results of the treatment revealed no negative clinical impact of L-HOBT supportive therapy on the body of the animals. At the same time, postoperative wounds after L-HOBT healed faster and with fewer postoperative complications compared to the control group. This resulted in a shorter treatment period, terminating with an earlier skin suture removal.