Magnetic spinel ferrite nanoparticles possess high scientific attention for the researchers attributed to its broad area for biomedicine purposes, comprising cancer magnetic hyperthermia and targeted drug delivery. Herein, we report the ultrasound irritation assisted the sol-gel method for the spinel Zn 0.5 Co 0.5x Ag 2x Fe 2 O 4 (x = 0.00, 0.10, 0.20, and 0.30) nanoparticles (NPs) synthesis. The Rietveld refinement patterns revealed the successful synthesis of the cubic structure Zn 0.5 Co 0.5-x Ag 2x Fe 2 O 4 and the crystallite size ranged from 14.1 nm to 18.4 nm. Also, the optical band gap decreased from 2.39 eV for Co-Zn ferrite to 2.20 eV for Zn 0.5 Co 0.2 Ag 0.6 Fe 2 O 4 sample. Electron paramagnetic resonance spectroscopy was used to study ferromagnetic resonance characteristics of the Zn 0.5 Co 0.5-x Ag 2x Fe 2 O 4 samples. The resonance field was increased from 2512.2 Gauss for Co-Zn ferrite sample to 2834.8 Gauss for Zn 0.5 Co 0.2 Ag 0.6 Fe 2 O 4 sample, while the line width decreased from 2401.3 to 1990.1 Gauss. Also, the saturation was reduced from 45.68 emu.g -1 for the pristine Zn 0.5 Co 0.5 Fe 2 O 4 sample to 22.20 emu.g -1 for Zn 0.5 Co 0.2 Ag 0.6 Fe 2 O 4 sample. Furthermore, cytotoxicity of Zn 0.5-Co 0.2 Ag 0.6 Fe 2 O 4 NPs against human breast cancer MCF-7, HepG2 liver cancer, and LoVo colorectal cancer cells was examined. The cytotoxicity of Zn 0.5 Co 0.2-Ag 0.6 Fe 2 O 4 on the previous cancer cell lines resulted in inhibition of cell growth estimated by MTT assay.