We report the synthesis of nominal 2 and 5 at.% Mn-doped ZnO nanocrystalline particles by a co-precipitation method followed by calcination at different temperatures. Transmission electron microscopy study and the Rietveld refinement of X-ray diffraction data revealed that these samples crystallize in the monophasic wurtzite structure. DC magnetization measurements of these samples, calcined at 675 K, showed that while nominal 2 at.% Mn-doped ZnO is ferromagnetic above room temperature, 5 at.% Mn-doped ZnO exhibited a paramagnetic behavior. A distinct ferromagnetic resonance (FMR) signal observed in the EPR spectra of 2 at.% Mn-doped ZnO further confirmed its room temperature ferromagnetism. EPR measurements were used to estimate the number of spins participating in ferromagnetic ordering of these compounds.