In this present paper, we report catalytic decomposition of methane over Ni/HY catalysts, with varying Ni loading at 550 degrees C and atmospheric pressure. The relationships between catalyst performance and characterization of the fresh and used form of catalysts are discussed from the data obtained by scanning electron microscopy, X-ray diffraction analysis, temperature programmed reduction, O-2 pulse chemisorption and carbon elemental analyses. It is observed that, the catalytic activity of Ni/HY catalysts is high at initial stages and gradually decreased with time and finally deactivated completely. The yield of hydrogen and carbon nanofibers is strongly dependent on Ni loading. It is found that 20 wt% Ni/HY catalyst showed higher hydrogen yield over the other loadings.