Optical, photocatalytic activity, and radiation shielding studies were conducted on CrxCo0.8Zn0.2Fe2-xO4 (0.0 ≤ x ≤ 0.1, Δx = 0.02) nanoferrites for water treatment and radiation shielding applications. The optical absorption analysis revealed that the optical band gap energy values range from 1.864 to 1.803 eV as assessed through Tauc plots. Further analysis of photocatalytic degradation showed that the Cr0.06Co0.8Zn0.2Fe1.94O4 sample exhibited superior methylene blue (MB) dye removal compared to other samples, with an efficiency of 96.74% in 60 min. Additionally, the present nanoferrites exhibited excellent stability in photocatalytic degradation over multiple cycles. The study also investigated the linear attenuation coefficient (LAC) of the current ferrite nanoparticles, demonstrating increased LAC values with higher Cr content, while the half value layer (HVL) diminished with further Cr concentration. The HVL values indicated the potential efficacy of our nanoferrites as radiation shields when compared to standard radiation shielding materials. Overall, this research suggests a new direction for optimizing spinel nanomaterials for applications in water treatment and radiation shielding.