Pd-Ni thin films were grown on porous substrates by metalorganic chemical vapor deposition (MOCVD) using the Pd-and Ni-acetylacetonate mixed precursor. Porous alpha-Al2O3 disks with and without gamma-Al2O3 top layer deposited by a sol-gel process were employed as substrates. The composition of the films was very close to the Pd/Ni ratio in the mixed precursor as shown by X-ray photoelectron spectroscopy (XPS) analysis. The microstructure and surface morphology of the Pd-Ni thin film was determined by using scanning electron microscope (SEM) and atomic force microscope (AFM). The porous substrates have a remarkable effect on the film morphology, which contributes to different hydrogen sensing properties. The deposited film on a porous alpha-Al2O3 substrate was porous and discontinuous due to the large pores of the substrate used, and the sensitivity to hydrogen is significantly larger than that of Pd-Ni thin film sensors reported in the literature. On the contrary, the deposited film on porous gamma-Al2O3 surface with bright metallic mirror provided a more uniform and compact thin film, and the sensitivity to hydrogen is much lower than that of the film on porous alpha-Al2O3 and blisters are easily formed under hydrogen atmosphere.