Spinel ferrites at nanoscale showed quite different properties rather than the bulk counterpart. Among all the ferrites, ZnFe2O4 compound is chemically stable and showed very good properties at room temperature. In this investigation, we reported the synthesis and characterization of ZnFe2O4 single-phase crystals of diameter 11 nm by solvothermal reflux method. Temperature-dependent dielectric constant, dielectric loss, and ac-electrical conductivity of the pellet were measured up to 450 °C under different alternating electric field frequencies from 1 kHz to 1 MHz. The obtained data revealed interfacial or space charge polarization mechanism. Furthermore, the sample showed superparamagnetic nature at room temperature. In addition, the magnetic hyperthermia value and specific heat generation rate (SHGR) of 128.76 J s−1 g−1 for ZnFe2O4 compound at 1 mg mL−1 concentration were evaluated. The data were interpreted by spin-relaxation mechanism. ZnFe2O4 nanoparticles showed good photocatalytic activity under UV light irradiation. The data were interpreted by electron–hole pair and radical formation and degradation of Rhodamine B dye. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.