Objective: To explore the effects of hyperbaric oxygen (HBO) treatment on the migration and differentiation of endogenous neural stem cells (NSCs) in neonatal rats with hypoxic-ischemic brain damage (HIBD). Methods: Seven-day-old Sprague-Dawley rats were randomly divided into the normal control (CON), the HIBD model and the HBO groups (HBO treatment was administered at 2 ATA, once daily for 7 days within 3 hrs after HIBD). HIBD model was prepared according to the classic Rice-Vannucci method. BrdU/DCX, BrdU/β-tubulin, BrdU/GFAP and BrdU/O4 immunofluorescence were examined by confocal microscopy in the subventricular zone (SVZ) and the cortex 7, 14 and 28 days after HBO treatment. Results: The BrdU+ DCX+ cells in the SVZ (84 ± 21 cells/mm2) in the HBO group were significantly higher than those in the CON group (39 ± 14 cells/mm2) (P < 0.05) and the HIBD model group (68 ± 17 cells/mm2) (P < 0.05) 7 days after HBO treatment. Fourteen days after HBO treatment, the BrdU + DCX+ cells decreased in the SVZ and more cells were observed in the cortex in the HBO group as compared with the CON group (P < 0.01). The BrdU+ β-tubulin+, BrdU+ GFAP+ and BrdU+ O4+ cells were observed in the cortex, and more BrdU+ β-tubulin+ and BrdU+ O4+ cells were observed in the HBO group as compared with the CON and the HIBD model groups (P < 0.05) 28 days after HBO treatment. Conclusions: HBO treatment may promote endogenous NSCs to migrate to the cortex and differentiate into mature neurocytes in neonatal rats with HIBD.