The glass-ceramic materials containing zinc ferrite nanocrystals, obtained from the 35SiO2 - 25CaO - 7P2O5 - 3Na2O - 10ZnO - 20Fe2O3 (wt.%) glass, was studied. The samples were investigated by DTA, XRD, FE-SEM, OMI, and VSM magnetometry. After melting process of raw materials, thermal behavior of glassy samples was investigated by DTA and necessary conditions for heat treatment of glassy samples at 700, 850, and 1050 °C were determined. The results showed that after heat treatment of the amorphous samples at 700 °C, a glass-ceramic containing zinc ferrite nanocrystals and traces of other phases such as wollastonite and calcium phosphate were formed. By heat treatment at 850 and 1050 °C, although the magnetic properties were enhanced, the zinc ferrite nanoparticles were gradually replaced by micron-sized particles of magnetite and maghemite, whereas the observed crystalline phases (wollastonite and calcium phosphate) were moderately replaced by fayalite and other silicate phases.