Background: Diabetic limb ulcers are highly prevalent and contribute to a significant increase in cost for the treatment of these patients in health services. However, healing of these wounds is a major health problem and may even lead to amputation. The primary aim of the current study is to evaluate the efficacy of hyperbaric oxygen therapy (HBOT) in facilitating the healing of diabetic foot ulcers, in addition to secondarily evaluating whether it reduces the number of amputations and improves the quality of life in these patients.Methods: A non-blind randomised clinical study will be conducted in the city of Imperatriz, Maranhão state, Brazil from 2019 to 2020, in diabetic patients with chronic foot ulcers (classified as Wagner grade 2, 3, and 4, persisting for more than one month). The outpatient follow-up for diabetic foot patients will be done at the Unified Health System, with a sample size of 120 patients (the randomisation allocation will be 1:1, being 60 patients for each arm). Half of the patients will receive standard treatment, i.e. dressings, debridement, antibiotics, and load relief, along with HBOT (HBOT group), and the other half will receive only standard treatment (control group). The patients of the HBOT group will be evaluated upon admission, after 10, 20, 30 and 35 HBOT sessions, and after six months and one year. The patients of the control group will also be evaluated at equivalent periods (upon admission, after 2, 4, 6 and 7 weeks, six months and one year). The SF-36 quality of life questionnaire will be filled upon admission and after three months of follow-up in both groups. The primary and secondary endpoints will be assessed with 1 year of follow-up.Discussion: Diabetic foot ulcers are a highly prevalent complication of diabetes with serious consequences. A study to assess the efficacy of HBOT in healing the ulcers and reducing the rate of amputations in diabetic patients is justified, which will eventually aid in the development of guidelines for treating these ulcers. Trial registration: Registration number RBR-7bd3xy. Registered 17 July 2019 – Retrospectively registered, http://www.ensaiosclinicos.gov.br/rg/RBR-7bd3xy