The effect of CuO on the sintering temperature, microstructure, and the microwave dielectric properties of (Zr0.8Sn0.2)TiO4 (ZST) has been investigated. The microwave dielectric properties of the ZST ceramics have been measured at cryogenic temperatures (15-290 K). The crystallite sizes of the sintered ZST ceramics are in the 30-50-nm range. The addition of CuO effectively reduced the sintering temperature to 1300 degrees C due to the liquid-phase effects. The addition of CuO did not cause any secondary phases up to 1.5 wt% of CuO. It is found that the quality factor (Q) of the sample without CuO decreased with an increase in temperature, whereas the samples with the addition of CuO up to 1.0 wt% showed less dependence on temperature at cryogenic temperatures. The microwave dielectric properties of the ZST ceramics measured at cryogenic temperatures exhibited a Q factor of 15 000 for pure ZST and 11 800 for ZST with 0.5 wt% of CuO at 15 K. The increase in Q factor at cryogenic temperatures can be attributed to the reduction in both intrinsic and extrinsic losses in the ZST ceramics.