Novel Ba-3(VO4)(2)-Mg2SiO4 microwave dielectric composite ceramics with compositions of (1-x)Ba-3(VO4)(2)-xMg(2)SiO(4) (x=0.50-0.65) have been prepared by firing mixtures of Ba-3(VO4)(2) and Mg2SiO4. X-ray diffraction and scanning electron microscopy analysis revealed that they coexist without forming secondary phases. Because their resonant frequency temperature coefficients (tau(f)) have opposite signs, the tau(f) of the composite ceramic can be adjusted passing through zero by changing the relative content of the two phases. Dielectric property measurements were performed using the resonator method at around 11 GHz. Ceramics with Mg2SiO4 55 wt% sintered at 1175 degrees C exhibited microwave dielectric properties of dielectric constant epsilon(r)=9.03, Q x f=52 500 GHz, and tau(f)=0.6 ppm/degrees C at 11.3 GHz. In this composite ceramic, we observed that the formation of the MgSiO3 secondary phase was suppressed.