Microwave dielectric properties of (Zr0.8Sn0.2)TiO4 system have been investigated as a function of processing variables such as the amount of Nb2O5, sintering temperature and atmosphere. The unloaded Q and dielectric constant were increased up to 1.0 mlo Nb2O5 because of the elimination of oxygen vacancies and the increase in a density and grain size. The maximum value of the unloaded Q was shifted toward a lower Nb2O5 content, with increasing oxygen partial pressure during sintering, while the dielectric constant showed the maximum value at 1.0 m/o Nb2O5 irrespective of sintering atmosphere. The temperature coefficient of resonant frequency depended more on the amount of additives than on sintering temperature. The microwave dielectric properties also varied with the kinds of additives even though the additives had similar ionic size and the same valence.