Rhodamine B (RhB), as perilous contaminants vastly utilized in industrial purposes, has potential role in environmental pollution. In present study a series of nanocrystalline rare earth (Sm3+) substituted magnesium-zinc ferrite with composition Mg0.2Zn0.8SmxFe2-xO4; (0 ≤ x ≤ 0.2) (MZS), for RhB degradation, were scrutinized. The sharpness and prevalence of XRD peaks emphasize its nanocrystalline nature. The lattice constant (aexp) is found to increase from 8.3818 to 8.4215 Å; obeying Vegard's law, with (311) peak shift from 2θ = 35.28ο to 34.32°. Bond dissociation energy of (Sm–O) is the reason for why the crystallite size (DWH) of MZS nanoferrites was increased by Sm/Fe substitution process; declaring an inverse relation between DWH and aexp values. Triple factors; magnetic moment of Sm/Fe cations in octahedral sites, crystallite size and porosity are responsible for the decrement behavior of saturation magnetization. The coercivity has a unique attitude; firstly exhibits a downward behavior and then an upward one. The dielectric parameters have unique behavior with Sm3+ substitution; firstly decrease (0.0 ≤ x ≤ 0.12) and then increases (0.12 ≤ x ≤ 0.2); governed by substitution ions, porosity and crystallite size effects. Nyquist plots have a distinct arc; meanwhile the second one is wholly unseen, due to one of two prospects. The optical energy gap has a special behavior; it has a blue shift from (1.74eV–2.06eV; for 0.0 ≤ x ≤ 0.12), and then a red shift from (2.06 eV–1.61 eV; for 0.12 ≤ x ≤ 0.2) by two justifications. The photo-decolorization efficiency of RhB over MZS photocatalysts is enhanced; (10.76%, 22.05%, 38.08%, 58.93%, 77.10% and 94.13% with increasing Sm3+ content, respectively) compared with its modest value 4.91% without addition. All these outcomes could provide insight into electronic devices besides photocatalyst for RhB removal by Mg0.2Zn0.8Sm0.2Fe1.8O4 ferrite nanoparticles.