Aluminum nanoparticles are considered promising as alternatives to conventional ink materials, replacing silver and copper nanoparticles, due to their extremely low cost and low melting temperature. However, a serious obstacle to realizing their use as conductive ink materials is the oxidation of aluminum. In this research, we synthesized the oxide-free aluminum nanoparticles using catalytic decomposition and an oleic acid coating method, and these materials were applied to conductive ink for the first time. The injection time of oleic acid determines the size of the aluminum nanoparticles by forming a self-assembled monolayer on the nanoparticles instead of allowing the formation of an oxide phase. Fabricated nanoparticles were analyzed by transmission electron microscopy and x-ray photoelectron spectroscopy to verify their structural and chemical composition. In addition, conductive inks made of these nanoparticles exhibit electrical properties when they are sintered at over 300 degrees C in a reducing atmosphere. This result shows that aluminum nanoparticles can be used as an alternative conductive material in printed electronics and can solve the cost issues associated with noble metals.