Owing to its high storage capacity (10.8 mass %), sodium borohydride (NaBH4) is a promising hydrogen storage material. However, the temperature for hydrogen release is high (>500 °C), and reversibility of the release is unachievable under reasonable conditions. Herein, we demonstrate the potential of a novel strategy leading to high and stable hydrogen absorption/desorption cycling for NaBH4 under mild pressure conditions (4 MPa). By an antisolvent precipitation method, the size of NaBH4 particles was restricted to a few nanometers (