CdMoO4:Mn nanocrystals with a tetragonal crystal structure were prepared by aqueous coprecipitation method at a low temperature of 2 degrees C under different pH values. The size of the CdMoO4:Mn nanocrystals of spherical morphology, increases with the Mn dopant concentration from 35 to 55 run for pH = 4. The morphology could be tuned from nanocrystals to. microstructures consisting of smaller nanoparticles by the Mn concentration when the pH value of the precursor was increased to 8. The thermal stability of the luminescence and magnetic properties of the Mn-doped samples also depend on the pH and the doping level. The effects of the pH and dopant on the luminescence and magnetic properties, including magnetic susceptibility and electron paramagnetic resonance, were investigated. This approach contributes to better understanding of aqueous chemistry methods to control the growth of nanocrystals.