Structural, mechanical and ferromagnetic characteristics of hydrothermally synthesized Cd0.4Mn0.6XO nanocomposites were investigated. The characterization of Cd0.4Mn0.6XO was accomplished using XRD, TEM, FTIR, photoluminescence and VSM techniques. The XRD showed the formation of monoclinic Cd2Mn3O8 alongside other phases. The crystallite size has no systematic trend against the valence state of ions. The particle size has minimum value (9.75 nm) for ZnO, and maximum values of 31.39 nm and 35.61 nm were observed for Al2O3 and Fe2O3, respectively. Similarly, typical enhancements are achieved for the mechanical and ferromagnetic parameters, e.g. they are increased when ZnO is replaced by Al2O3 and significantly enhanced by Fe2O3. In contrast, they were reduced by the other X, but they are still higher than ZnO. The photoluminescence of Cd0.4Mn0.6XO shows violet, blue, green, and orange emissions. The reported results indicate a strong correlation between the mechanical and ferromagnetic properties of nanocomposites against the particle/crystallite sizes and valence state.