Background: The traditional treatment of soft tissue injuries consists of the RICE protocol - rest, ice, compression, and elevation, followed for up to 72 hours after a trauma. Although designed as an immediate therapy to reduce inflammation that occurs after an acute injury, the RICE protcol might not be the best way to promote healing due to limiting blood flow. Molecular hydrogen (H 2) has recently been put forward as a possible adjuvant treatment in musculoskeletal medicine, yet limited data are available concerning its effectiveness as a first-aid intervention. Case report: We report here a case of an elite professional athlete who suffered a grade II ankle sprain, and who subsequently received six sessions of ankle and foot hydrotherapy (e.g. 30-min at every four hours) with super-saturated hydrogen-rich water during the first 24 hours post-injury. The pain VAS self-completed by the patient dropped from 50 points (moderate pain) at baseline (immediately after injury) to 20 points (mild pain) at 24-h follow-up. Ankle swelling dropped by 2.8% and dorsiflexion range of movement improved by 27.9% from baseline to follow-up, respectively. Conclusions: Our case has indicated that an acute multi-session hydrotherapy with hydrogen-rich water might be a helpful treatment in terms of pain, swelling reduction and regaining range of motion after an ankle sprain.