Background Genitourinary syndrome of menopause (GSM) is a condition affecting many postmenopausal women. Among the available treatments, the vaginal natural oxygenation device (VNOD) is a new promising option. Aim To evaluate the safety and the effectiveness of vaginal high concentration (HC) oxygen (O2) and hyaluronic acid (HA) in postmenopausal women with vaginal atrophy (VA). Methods Study 1: Ten subjects received HA and O2 at a concentration of 21% (sham group) and ten at 95% (treatment group). All subjects completed five sessions of VNOD. Evaluations and questionnaires were completed at baseline, before each session and at one-month follow-up: Visual Analogue Scale, Vaginal Health Index (VHI), Vaginal Maturation Value (VMV), Menopause Quality Of Life (MeNQoL), Female sexual function index (FSFI) and Female sexual distress scale (FSDS). Study 2: 52 postmenopausal women with VA completed the same protocol of study 1 with HC O2 and HA. Results Treatment was well-tolerated. In study 1, in the treatment group we recorded significant improvements in VHI score ( p-value 0.001), VMV ( p-value 0.005) and in the psychosocial, physical and sexual domains of the MeNQoL compared to sham group. In study 2, all women experienced a significant improvement in VHI ( p-value <0.001), FSFI total score ( p-value 0.007), desire ( p-value 0.004), lubrication ( p-value 0.006), satisfaction ( p-value 0.042), pain ( p-value 0.001) domains, FSDS score ( p-value 0.003) and MeNQoL sexual domain ( p-value <0.001). Conclusion The preliminary results of this study suggest that VNOD is a safe and effective treatment for VA in postmenopausal women, and improves sexual function.