MnxCo1-xFe2O4 nanoparticles with compositions x = 0, 0.25, 0.50, and 0.75 were synthesized using a straightforward surfactant-free solvothermal route. The nanoparticles' microstructure, morphology, and size distribution were studied by X-ray diffraction and transmission electron microscopy. Raman spectroscopy was used to obtain information about their vibrational properties and the cation distribution in the spinel lattice. UV–visible and diffuse reflectance spectroscopy were used to study their photocatalytic activity and optical properties. The behavior of MnxCo1-xFe2O4 nanoparticles in an aqueous medium and its effects on the photocatalytic activity were highlighted by ζ-potential measurements. Their magnetic properties were investigated using M − H curves and ZFC-FC measurements. The results allowed us to study the solvothermal route's effectiveness for synthesizing well-crystallized ultra-small size MnxCo1-xFe2O4 nanoparticles with promising photocatalytic and superparamagnetic properties. They also provided insights into the effects of manganese's cobalt substitution on the spinel lattice's cation distribution and the mechanisms behind their observed physical properties.