We report the use of hyperbaric oxygen (HBO) therapy to treat the complication of necrotizing fasciitis following Cesarean section in a postpartum gravida with diabetes mellitus. Our patient was a 25-year-old, gravida 1, para 1, woman with a history of type 1 diabetes mellitus since the age of 18. The patient experienced preterm labor at 31+1 gestational weeks and was treated with magnesium sulfate for tocolytic therapy. The patient then went into labor at 39+6 gestational weeks. She received Cesarean section due to prolonged labor associated with non-reassuring fetal status of both smooth baseline and fetal tachycardia. An ultrasound scan of the lower abdomen on the 4th postoperative day revealed fluid collection measuring 4 mm over the rectus fascia and edematous change of the surrounding soft tissues under the Cesarean section incision site. The patient eventually received HBO for a total of 7 days. Following HBO, the condition of the surgical wound improved dramatically. The results of this case showed that HBO has the potential to be a cost-effective way to enhance the healing of necrotizing fasciitis in diabetes mellitus gravida.