Because of large differences in the processing temperature windows between ceramics and polymers, the single-step co-sintering of microwave dielectric ceramic-polymer substrates remains challenging. In this work, a dense (Ca 0.65 Bi 0.35 )(Mo 0.65 V 0.35 )O 4 (CBMVO) ceramic was first prepared through cold sintering at 150 • C, under a uniaxial pressure of 300 MPa for 60 min with Li 2 MoO 4 (LMO) as a transient low-temperature solvent. Cold-sintered CBMVO-5 wt% LMO ceramic shows excellent microwave dielectric properties: ε r ∼ 11.4, Q × f ∼ 7070 GHz, τ f ∼ −7.4 ppm/ • C. Moreover, the optimized cold sintering process enabled the preparation of a layered co-sintered (2-2 type) CBMVO-polytetrafluoroethylene composite, which maintained excellent microwave dielectric properties and showed a good heterogeneous interface bonding. The proposed cold sintering co-firing of ceramic-polymer composites in a single step shows great potential for application in the seamless integration between ceramics and polymer substrates.