Ferromagnetic cobalt nanoparticles with average diameter of 9.5 nm, used for the purpose of magnetic catalyst recovery, were shown to catalyze the hydrolysis of silicon-hydride bonds for a range of hydrosilanes. The highest turnover frequencies (220-311 moles silane/moles Co/h) were observed for the dialkylsilanes (R2SiH2), which were hydrolyzed to give the corresponding dialkylsilanediols. The monoalkylsilanes (RSiH3) reacted more slowly (2-20 moles silane/moles Co/h) and gave an oligomeric product. Trialkylsilanes (R3SiH) required elevated temperatures in order to observe trace activity.