In this study, we have synthesized unique Mn0.5Zn0.5ErxYxFe1.8-2xO4 (x <= 0.1) SFNPs via ultrasonication (sonochemical) approach. Electrical and dielectric features of Mn0.5Zn0.5ErxYxFe1.8-2xO4 SFNPs were inspected comprehensively using impedance spectroscopy up to 3.0 MHz from 20 to 120 degrees C for a various substitution ratio of Er3+ and Y3+ ions. The fundamental electrical and dielectric parameters which are AC/DC conductivity, activation energy, dielectric loss, dielectric constant, and tangent loss were studied in the determined frequency and temperature ranges. The experimental results showed that ac conductivity obeys the power law equation and the value of n changes considerably with the co-substitution of Er3+ and Y3+ ions in various ratios, however, exhibiting some dependencies over a given temperature range. The DC conductivity and activation energy curves show a significant variation with temperature and co-substitutional ratios of Er3+ and Y3+ ions. The conduction mechanisms can essentially be assigned to the grain-grain boundaries. Therefore, frequency-dependent dielectric properties of Mn0.5Zn0.5ErxYxFe1.8-2xO4 SFNPs can be described by means of the Koop's model. It is revealed that conductivity and dielectric properties of Mn0.5Zn0.5ErxYxFe1.8-2xO4 SFNPs are adjustable with co-substitutional ratios of Er3+ and Y3+ ions.