0.8 Pb(Zr0.52Ti0.48)O-3-0.2 Pb(Zn1/3Nb2/3)O-3 (PZT-PZN) and 2 mol% Mn-doped PZT-PZN ceramics were investigated to deterministically identify the presence and effect of the secondary phase in controlling electrical properties. On the basis of the X-ray diffraction and energy dispersive spectroscopy analysis, we show that secondary phase in Mn-doped PZT-PZN is not MnO2 precipitate, but it is related to the formation of ZnO. This result was found to be consistent with the grain growth observed in the Mn-doped sintered ceramics and changes in ferroelectric behavior. We propose that Mn3+ substitution on Ti and Zr site induces hardening effect, whereas Mn2+ substitution on Zn-site stabilizes the perovskite phase in synthesis of PZT-PZN.