Synthesis of zinc ferrite (ZnFe2O4) by high-energy ball-milling from a powder mixture of zinc oxide (ZnO) and hematite (α-Fe2O3) is investigated. The millings are performed under air using tungsten carbide vials and balls. The spinel phase appears within 2 h grinding and the reaction is almost complete after 24 h. The broadening of X-ray diffraction lines shows that the crystallite size is around 10 nm. Mössbauer spectra indicate that there is some inversion in the ferrite, leading to the formula (Zn0.312+Fe0.693+)A(Zn0.692+Fe1.313+)BO42− for the 24 h sample. We also show that preliminary millings of the initial oxides (zincite and hematite) slow down the reaction. Finally, dilatometric studies show that the shrinkage proceeds in several steps, due to a grain size distribution in the sample.