In the present work, Co1-xZnxFe2O4 (x = 0.0, 0.3, 0.5, 0.7 and 1.0) nanoparticles were prepared by chemical co-precipitation method. Prepared Co1-xZnxFe2O4 ferrite powder was sintered at 900 °C for 4 h after TG-DTA thermal studies. XRD analysis revealed the single-phase cubic structure of Co–Zn ferrite nanoparticles and also studied the variation in structural parameter with increasing Zn concentration. The formation of the ferrite phase was confirmed by studying FTIR spectra. The SEM images shows the agglomeration of spherical grains due to the difference in the magnetic nature of the sample. Peaks of respective elements (Co, Zn, Fe, and O) in EDX spectra show the formation of cobalt zinc ferrite. Variation of energy band gap with increasing zinc concentration in cobalt ferrite studied by UV–Vis. Spectroscopy. The M − H loops revealed that the values of magnetic parameters such as MS, Mr, Hc, nB, and Mr/Ms ratio decrease with increasing Zn2+ content in cobalt ferrite nanoparticles. •Zn2+ substituted cobalt ferrite nanoparticles have been successfully prepared by wet chemical route.•XRD studies confirmed the formation of cubic spinel structure.•It's infrared, morphological, optical and magnetic properties were investigated.•Magnetic properties were influenced significantly by nonmagnetic Zn2+ ion substitution in cobalt ferrite.•Zn2+ ion substituted cobalt ferrite nanoparticles are desirable in biomedical applications.