Hydrogen transport studies were confined to molecular hydrogen driven permeation through two largely different polycrystalline grain structures: (i) microcrystalline nickel with an average grain size of 3µim and (ii) nanocrystalline nickel with an average grain size of 78 nm. Permeation experiments were conducted in a double chamber ultrahigh vacuum system separated by a test specimen. Hydrogen permeabilities and diffusivities through polycrystalline nickel were measured in the temperature range of 30°C to 200°C. At 30°C the nanocrystalline nickel displayed a six-fold increase in permeability with respect to the microcrystalline nickel. The enhancement in permeability is believed to be the result of enhanced intercrystalline volume fraction in the nanocrystalline nickel.