Five COVID-19 patients with increasing supplemental oxygen requirements received hyperbaric oxygen therapy (HBOT). An average of five treatment sessions of HBOT were given to the patients. All five patients were close to requiring intubation right before receiving HBOT. Post-HBOT, all of the patients exhibited increases in their previously low oxygen saturation levels, decreased levels of inflammatory markers, and resolution of tachypnoea. None of the patients required a ventilator. Three patients were discharged from the hospital in under a week after their final HBOT treatment session, and the other two patients are in stable conditions currently. No complications or side effects arose from the HBOT treatments. However, further research must be done to draw definite conclusions about the effectiveness of HBOT because there is not enough data to do so from this case series.