Abstract Polymer dielectric composites are fabricated by blending polyimide (PI) with poly(vinylidene fluoride) (PVDF) base on different temperature conditions. The dielectric and thermal properties of the composites are studied. Experimental results indicate that the dielectric properties of the composites are enhanced by increasing the reaction temperature, while all the resulted composites exhibit excellent thermal stability. Specifically, the sample showing optimized dielectric properties can be obtained at a reaction temperature of 50 °C.