In the present study, amorphous–nanocrystalline phase transformation induced by mechanical milling of full monolithic bulk metallic glasses (based on Zr65Al7.5Ni10Cu17.5 and Zr58Al16Ni11Cu15 alloys) has been investigated using X-ray diffraction as well as transmission electron microscopy. Nanocrystals having an FCC structure and a grain size of several 10 nm precipitate in the early stages of the milling process and remain stable for long milling duration. The structure changes induced by milling give a new insight on the preparation of amorphous-related alloys when using the method of mechanical milling.