Nanostructure formation of fully amorphous Al86Ni9Mm5 alloys in both as solidified amorphous and annealed nanocomposite conditions was investigated using XRD, DSC, and TEM. The exothermic reaction peak of DSC is associated with the crystallization of fcc-Al, Al3Ni, and A111Ce3 phase. The microstructure of annealed specimen at 250 oC consists of a random distribution of fine nanocrystalline fcc-Al crystals embedded in the amorphous matrix. During primary crystallization, partitioning of the solute atoms takes place at the interface, resulting in an increase of solute atoms in the amorphous and interdendritic resign. The final microstructure shows a homogeneous distribution of intermetallic compounds embedded in the Al matrix. The hardening effect of nanostructured specimens annealed at 250 oC is attributed to both solute enrichment in the amorphous matrix and formation of fcc-Al crystallites. The highest hardness of 490 Hv in this research is obtained in the specimen heat treated at 300 oC for 20 min.