Zinc ferrite is synthesized via mechano-activation, followed by thermal treatment. Spinel ZnFe2O4 single phase is confirmed by X-ray diffraction. SEM micrographs show large particles with average particle size〈Dpart〉=1μm, with particles in intimate contact. However, TEM micrographs show incrusted nanocrystallites at the particles surface, with average nanocrystallite size calculated as 〈Dinc〉≈5nm. The blocking temperature at 118K in the ZFC–FC curves indicates the presence of a superparamagnetic response which is attributable to the incrusted nanocrystallites. Moreover, the hysteresis loops show the coexistence of superpara- and paramagnetic responses. The former is observable at the low field region; meanwhile, the second one is responsible of the lack of saturation at high field region. This last behavior is related to a paramagnetic contribution coming from well-ordered crystalline microdomains.The hysteresis loops are analyzed by means of two different models. The first one is the susceptibility model used to examine separately the para- and superparamagnetic contributions. The fittings with the theoretical model confirm the presence of the above mentioned magnetic contributions. Finally, using the Langevin-based model, the average superparamagnetic diameter 〈DSPM〉 is calculated. The obtained value 〈DSPM〉=4.7nm (∼5nm) is consistent with the average nanocrystallite size observed by TEM.