The development of electrical insulators that are thermally conducting is critical for thermal management applications in many advanced electronics and electrical devices. Here, we synthesized polymer nanocomposite (PNC) films composed of polymers [polyethylenimine, poly(vinylamine), poly(acrylic acid), and poly(ethylene oxide)] and dielectric fillers (montmorillonite clay and hexagonal boron nitride) by layer-by-layer technique. The cross-plane thermal conductivity [Formula: see text] of the film was measured by the 3ω method. The effect of various factors such as film growth, filler type, filler volume fraction, polymer chemical structures, and temperature on the thermal conductivity is reported. The [Formula: see text] of PNCs with thickness from 37 nm to 1.34  μm was found to be in the range of 0.11 to 0.21 ± 0.02 W m−1 K−1. The [Formula: see text] values were found to be lower than the constituent polymer matrix. The experimental result is compared with existing theoretical models of nanocomposite systems to get insight into heat transfer behavior in such layered films composed of dielectrics and polymers.