Aluminum–organic composite nanoparticles were synthesized by a modified Haber and Buhro’s process; ethylene glycol (EG) was used as solvent instead of 1,2,3-trimethyl benzene. The use of EG caused an extremely active reaction in the preparation of aluminum nanoparticles, and the subsequent polymerization of EG to produce polyethylene glycol (PEG) occurred on the prepared aluminum nanoparticle surface due to the active reaction. Carboxylic agent passivation on the surface of the prepared Al–PEG particles was successfully performed, and TEM and FT-IR analyses clearly showed that the resulting prepared particles, which had a geometric mean diameter of ∼55nm, consisted of an aluminum core and PEG and oleic acid layers. As result of a floating test performed for seven days, the resulting prepared Al–PEG–oleic acid composite nanoparticles showed good properties in the inhibition of oxidation and humidity absorption.