A systematic investigation on the structural and magnetic properties of transition metals (M=Mn, Ni, Fe and Cu) doped Co0.1Zn0.9O (M0.1Co0.1Zn0.8O) nanoparticles synthesized by an easy and inexpensive microwave-assisted combustion method is presented. X-ray diffraction (XRD) and HR-SEM results show single phase nature with hexagonal wurtzite structure, and reveal the incorporation of metal ions into the lattice positions of Zn ions in CoZnO lattice. Size of the nanoparticles was found to vary between 25.3 nm and 33.5 nm. The magnetization measurements result into ferromagnetic state for all doped samples. Saturation magnetization varies with the type of doped ions indicating the role of interaction between doped ions and Co ions. Ferromagnetic interaction enhances at low temperatures and remains non-zero above room temperature as suggested by magnetization vs. temperature measurements. The room temperature ferromagnetism of the samples was attributed to the exchange interactions between free delocalized carriers (holes from valance band) and the localized d spins of doped transition metal ions. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.