<p>This study investigates the microwave dielectric properties of In₂Mo₃O₁₂ ceramics synthesized through a solid-state reaction method, emphasizing their potential applications in low-temperature co-fired ceramics (LTCC). X-ray diffraction (XRD) analysis confirmed that all samples crystallized in an orthorhombic structure within the Pbcn space group. The influences of bond ionicity, lattice energy, and bond energy on dielectric properties were thoroughly assessed. Additionally, a significant correlation between the Full Width at Half Maximum of the principal Raman peak and the <i>Q</i> × <i>f</i> value was observed, offering valuable insights into the material’s performance.</p><p>Remarkably, the specimen sintered at 750&#xa0;°C exhibited excellent microwave dielectric characteristics, including a low relative permittivity (<i>ε</i>_<i>r</i>) of 6.28, Q-factor multiplied by frequency (<i>Q</i> × <i>f</i>) value of approximately 2200&#xa0;GHz, and a negative temperature coefficient of resonant frequency (<i>τ</i>_<i>f</i>) of -131.8&#xa0;ppm/°C. These properties, particularly the low permittivity, underscore the potential of In₂Mo₃O₁₂ ceramics as efficient passive components in 5G applications, such as millimeter-wave devices for LTCC technologies. Furthermore, the P–V-L analysis deepens the understanding of the material’s dielectric behavior, fostering its integration into advanced communication systems and enhancing the performance of next-generation electronic devices.</p>