Mn-doped samples were used to study the effects of Mn dopant on the dielectric properties of PFW ceramics, especially on its aging behavior, since they could add some knowledge on the role of lattice defects on the aging mechanisms of this relaxer ferroelectric. Mn doping does not cause marked changes in the maximum of permittivity (epsilon(rmax)), transition temperature (T-0), and diffuseness coefficient (delta) under the solubility limit, whereas the resistivity increases significantly with increasing the Mn content. Mn-modified PFW ceramics exhibit evident aging behavior and its level increases with the increase in Mn content. The aging shows strong dependence on the frequency and has a loglinear function of aging time. Probable lattice defects in the ceramics are discussed and it is suggested that the acceptor Mn ions are dominantly compensated by oxygen vacancies, providing reorientable dipole pairs which are responsible for the aging process of Mn-modified PFW ceramics.