Samples of nickel-supported alumina were prepared from Sol-gel and non-sol-gel alumina by impregnation of aqueous solution of nickel formate and the decomposition behavior of the nickel formate on alumina was then followed by combined thermal analysis and infrared spectroscopy. The decomposition products were characterized by X-ray photoelectron spectroscopy, time-of-flight secondary-ion mass-spectroscopy, and scanning electron microscopy. The surface areas and pore distributions were measured by BET. Nickel formate was found to decompose over a wide temperature range owing to its interaction with the alumina. The surface area of the Sol-gel alumina after nickel loading increased whereas the non-sol-gel alumina remained unchanged. The products were amorphous, and they had a pore distribution in the mesoporous region. The nickel species existed as nickel aluminate, unsupported nickel oxide, stoichiometric nickel oxide, and metallic nickel. The nickel species were uniformly distributed on the surface. The particles agglomerated at the submicron level; no nickel species was found on the surface.