Nano-ferrites with chemical equation CuxZn1-xFe2O4 (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6 and 0.7) were prepared by sol–gel auto-combustion method to study structural and magnetic properties along with antibacterial and antifungal activity. The samples are sintered in air at 400 °C for 4 h. The samples are characterised by x-ray diffraction (XRD), ultraviolet (UV), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), energy dispersive X-ray (EDX), and vibrating-sample magnetometry (VSM) tools. Presence of some secondary phases are noticed in the samples. XRD data is utilised to calculate lattice parameter, crystallite size, lattice strain, and density of ferrite samples. The crystallite size varies between 6.3 and 7.7 nm and lattice strain has value between 0.11–0.15. Also, VSM is used to calculate saturation magnetisation, coercivity and remanent magnetisation of synthesised samples. The saturation magnetisation as high as 32.8 emu g−1 is obtained for x = 0.7 composition. The magnetic CuxZn1-xFe2O4 nanoparticles have shown good antibacterial and antifungal activity.