Abstract H 3 BO 3 was used as the sintering additive to enable Zn 0.997 Cu 0.003 ZrNb 2 O 8 ceramics to accomplish low‐temperature sintering and outstanding microwave dielectric performances. Composite ceramics were created using typical solid‐state processes. The effects of added H 3 BO 3 on the sintering behavior, microstructural characteristics, vibrational properties, and microwave dielectric performances of Zn 0.997 Cu 0.003 ZrNb 2 O 8 + x wt% H 3 BO 3 (2 x 8) ceramics have been systematically investigated by means of X‐ray diffraction, Raman scattering spectroscopy, scanning electron microscopy, and complex chemical bond theory. The results of relative density and microscopic morphology demonstrated that the application of an adequate quantity of H 3 BO 3 additive can significantly enhance sintering properties. The doped H 3 BO 3 alters the inter‐ionic interactions so that the structural features become intrinsic to the microwave dielectric performances. The particularly satisfactory microwave dielectric performances ( = 10.61, = 33 980 GHz, and = ‐45.10 ppm/°C) were detected in x = 6 ceramic specimens sintered at 950°C, which would make it promising for use in modern low temperature co‐fired ceramics technology.