Nano zinc manganite (ZnMn2O4) samples have been prepared using hydrothermal method in presence and absence of surfactants. The samples were characterized by XRD, FT-IR, and electron microscopy (SEM) as well as (TEM). Catalytic activity for investigated samples as well as, dc- and ac-electrical conductivity as a function of frequency and temperature were studied. Gamma radiation effect on the studied properties is investigated. All samples showed tetragonal spinel structure with average crystallites sizes lay in the range 19 – 90 nm. The samples showed semiconducting behavior in which the electrical conduction occurred via electron exchange amongst manganese ions situated on octahedral sites in the spinel structure. The particle size, morphology, electrical and catalytic activity were affected by each of preparation conditions and gamma– irradiation process.