The new coronavirus SARS-CoV-2 produced the COVID-19 pandemic. Acute respiratory distress syndrome (ARDS) is caused by this highly infectious virus, which infects both the lower as well as the upper respiratory tracts. Even with COVID-19 patients, the HBOT has proven to be an effective means of treating hypoxia. PURPOSE: to examine the impact of hyperbaric oxygen on forced vital capacity (FVC), forced expiratory volume (FEV1) in addition to oxygen saturation in post- COVID-19 patients. DESIGN:patients were assigned randomly in to two equal groups by randomized controlled trial. SETTING: Patients with post Covid-19 from inpatient Clinic ZagaZig Chest Hospital sharqia governate Ministry of Health. SUBJECTS: seventy-two patients (21 to 66 years old) previously infected with SARS-CoV-2. METHODS: Patients were randomized into two equivalent groups utilizing a computer-generated block randomization program, Hyperbaric Oxygen therapy in addition to breathing exercises and traditional medical treatment were given to Experiamental group "A", and the same traditional medical treatment program were given to Control group "B" throughout the course of an 8-weeks of intervention. The patients' pre- and post-treatment evaluations were performed using body weight and height scale for measuring weight and height then calculating BMI, Spirometry for measuring FVC, FEV1, Pulse Oximeter for Oxygen. RESULTS: Mixed design MANOVA comparisons revealed statistically significant differences among pre- and post-treatment for all variables in both groups as p-value <0.05. Between both groups, analysis revealed that the study group had statistically significant improvement over the control group (p-value <0.05) when comparing the two groups. CONCLUSION: HPOT has a positive effect on the Pulmonary Functions in Post COVID-19 Patient.