Porous silicon powder has been fabricated from an Al–Si alloy by etching in strong acids, and its hydrogen storage capacity has been studied. Double acid etching in the fabrication and nickel blending have been proposed to further enhance the hydrogen storage capacity of the etched powder. The etching effectively removed the aluminum from the Al–Si alloy to form a porous Si structure, with a large increase in surface area. After charging under a hydrogen pressure of 3.7 MPa at 150 °C, the hydrogen uptake of double-etched and Ni-blend porous silicon samples was 0.81 wt%, which was >13 times higher than that of the as-received Al–Si alloy (0.06 wt%). The percentage of retained hydrogen after desorption was also largely decreased. The results of this study provide strong evidence on the potential of using porous silicon powder from Al–Si alloy as a cost-effective solid-state storage material for hydrogen.