An investigation has been performed into the influence of Sm3+ substitution on the structural, optical, and magnetic characteristics of Co0.5Mn0.5SmxFe2–xO4 (x = 0.0-0.1 and x changes at a step of 0.02) and its prospective use as an effective photocatalyst. The examination also explored the potential use of this composition as a proficient photocatalyst. The structural results verified the production of cubic spinel structures in all compositions. The determination of crystallite size has been done via the Williamson-Hall approach, taking into account the influence of strain variables. The ferrite nanoparticles’ spherical form was identified via transmission electron microscopy (TEM) examination. The Co0.5Mn0.5Fe2O4 sample exhibited a particle size distribution of around 40 nm. The optical band gap, ascertained using UV–vis-diffuse reflectance (DRS)spectra analysis, ranged from 1.38 to 1.43 eV. Vibrating sample magnetometer (VSM) analysis revealed that the produced sample was soft magnetic with moderate magnetization (58.18 emu g−1 - 42.73 emu g−1). Methylene Blue (MB) dye’s photocatalytic degradation (PCD)was used to study the photocatalytic behavior while exposed to sunlight. The Sm-doped Co-Mn nanoferrites synthesized in this study exhibit potential for use as effective active photocatalysts in the degradation of toxic industrial dyes. This application promises to enhance safety in both the environmental and healthcare sectors.