Radiation therapy for the treatment of head and neck cancer can injure normal tissues and have devastating side effects. Hyperbaric oxygen (HBO) is known to reduce the severity of radiation-induced injury by promoting wound healing. While most of the research in literature has focused on its efficacy in osteonecrosis, HBO has other proven benefits as well. The aim of this review was to identify the various benefits of hyperbaric oxygen therapy in patients who have undergone radiation for head and neck cancer. An electronic database search was carried out to identify relevant articles and selected articles were reviewed in detail. The quality of evidence for each benefit, including preserving salivary gland function, preventing osteonecrosis, dental implant success, and overall quality of life, was evaluated. Evidence showed that HBO was effective in improving subjective symptoms of xerostomia, swallowing, speech and overall quality of life. There was no conclusive evidence to show that HBO improved implant survival, prevented osteonecrosis, or improved salivary gland function. The high costs and accessibility of HBO therapy must be weighed against the potential benefits to each patient.