The effects of the Ta substitution for Nb and the Zr substitution for Ti on the microwave dielectric properties and crystal structure of Sm(Nb 1−x Ta x )(Ti 1−y Zr y )O 6 ceramics were investigated in this study. The Sm(Nb 1−x Ta x )TiO 6 (x=0–1) ceramics were single phase, whereas the limit of solid solutions for the SmTa(Ti 1−y Zr y )O 6 ceramics was y=0.4. In the case of the Sm(Nb 1−x Ta x )TiO 6 ceramics, the dielectric constant and the temperature coefficient of resonant frequency were decreased, whereas the quality factor was increased by the Ta substitution for Nb. The maximum Q·f value was obtained when the SmTaTiO 6 was synthesized, and the microwave dielectric properties are, ɛ r =37.6; τ f =24.2ppm/°C; and Q·f=24541GHz. On the other hand, the dielectric constants of the SmTa(Ti 1−y Zr y )O 6 ceramics were decreased from 37.6 to 28.9, whereas the quality factor was increased from 24541 to 38320GHz with increasing composition y from 0 to 0.4. The temperature coefficient of resonant frequency of the ceramics varied from 24.2 to −11.6ppm/°C. A near zero temperature coefficient of resonant frequency results from the composition of y=0.3 with a dielectric constant of 31.1 and Q·f value of 37481GHz.