We studied the effect of high manganese substitution at ZnO host lattice and report the optical and magnetic properties of Zn1-xMnxO (at x = 0.31, 0.50 and 0.62) nanoparticles (2-10 nm) prepared by the modified solvothermal method for the first time. Composition of these solid solutions was measured by ICP analysis. Solid solution of Zn0.69Mn0.31O (2 nm) was successfully synthesized, however at high dopant concentration (50% and 62% Mn) mixture of phases appeared instead of forming solid solution. UV-visible studies show the absorption edge at 385 nm for x = 0.31 and 0.50 which is slightly red shifted compared to pure ZnO, however Zn0.38Mn0.62O shows the presence of hausmannite phase of Mn3O4. Specific surface area of these nanoparticles was found to be 48, 100, and 47 m(2) g(-1). Magnetization measurements reveal that Zn0.69Mn0.31O and Zn0.50Mn0.50O show paramagnetic behaviour with antiferromagnetic coupling, however Zn0.38Mn0.62O shows ferrimagnetism. (C) 2012 Elsevier B.V. All rights reserved.