BACKGROUND/AIMSubdural hematomas (SDH), often caused by head trauma, are serious with high mortality and long-term complications. Studies show that molecular hydrogen has neuroprotective effects, such as reducing oxidative stress, inflammation, and cell death. It may also protect mitochondria, support cell function, and regulate immune responses, making it a promising new treatment option for SDH. However, more research is needed to confirm its effectiveness and create treatment guidelines.CASE REPORTWe present a 24-year-old man with SDH, along with a right-sided midline shift, uncal herniation, and dilated left pupil. Conventional treatments-craniectomy, hyperbaric oxygen, therapeutic hypothermia, and stem cell therapy-were essential for stabilizing his condition. In addition, we administered hydrogen capsules as a novel adjunct therapy, beginning daily treatment immediately upon admission. While recovery was primarily due to standard interventions, hydrogen therapy appeared to enhance immune markers, particularly Treg and plasma cells, with no adverse effects. This case indicates that hydrogen therapy may serve as a beneficial addition to established SDH management methods.CONCLUSIONThis case suggests that molecular hydrogen therapy may be a helpful adjunct treatment for SDH with midline shift. Conventional therapies, including craniectomy, hyperbaric oxygen, therapeutic hypothermia, and stem cell therapy, were vital to the patient's recovery, but hydrogen therapy may have contributed by modulating immune responses, particularly Treg and plasma cell activity. While these findings are encouraging, further research is necessary to confirm hydrogen therapy's benefits and its role alongside traditional neurocritical care treatments.