This study investigated the effects of the addition of Nb2O5 and sintering temperature on the properties of Bi2Mo2O9 ceramics. The ceramics were sintered in air at temperatures ranging from 620 degrees C to 680 degrees C. The addition of small amounts of Nb2O5 as a dopant significantly affected the crystalline phase and the microwave dielectric properties of the Bi2Mo2O9 ceramics. The secondary phase, -Bi2MoO6, was observed when Nb2O5 was added. However, unlike the Bi2Mo2O9 ceramic without Nb2O5 sintered above 645 degrees C, the ceramics with 3mol% Nb2O5 contained no -Bi2MoO6 when sintered at 660 degrees C. The Qxf value and f of the Bi2Mo2O9 ceramics were improved by Nb2O5 doping. The Bi2Mo2O9 ceramics doped with 2mol% Nb2O5 exhibited the best microwave dielectric properties, with a permittivity of 36.5, a Qxf value (f=resonant frequency, Q=1/dielectric loss at f) of 14100GHz and f of +5.5ppm/degrees C after sintering at 620 degrees C.