Copper vanadate (CV) and manganese vanadate (MV) exhibit magnetic and optical properties that have drawn the attention. Due to CV polymorphism and phase multiplicity, CV is common to exist as mixed phases. In this study, nanostructures of mixed-phase CVs mixed with MV were synthesized hydrothermally followed by calcination at 400 °C, with Mn mole fractions 0.0, 0.4, 0.6, 1.0. The uncalcined and calcined Mn-Cu vanadates (MCVs) were investigated by XRD, SEM, TEM, FT-IR, EDX, ICP-AES, TGA, DTA, DSC, BET, XPS, and VSM. XRD analysis shows co-existence of multi-phase CVs with MnV2O6 and V oxides. Electron micrographs show nanostructures of multiple morphologies (rods, cubes, sheets, and irregular). As Mn content increased in the MCVs, their thermal stability increased, optical bandgap (Eg) declined from 2.46 to 1.60 eV, and magnetism diverted from the superparamagnetic-like to paramagnetic (Hc from 1362 to 69 G and Mr/Ms from 0.430 to 0.003). Magnetism parameters of calcined MCVs were more labile to Mn content variation compared to the uncalcined MCV counterparts. Graphical Abstract