Abstract Thermal interface materials (TIMs) have been widely used in various electronic devices and are crucial for next generation electronics such as flexible electronics. Ultrathin full carbon films with extraordinary high thermal conductivity (k) and promising mechanical strength have been well documented, but the brittleness (elongation at break~0.5–3.0%) limits their practical applications. Besides high k, superior TIMs required excellent flexibility, low thickness and low hardness to ensure the thermal management capability. Herein, high-performance polymer composite films with the combination of high k ∥ (39.27 Wm-1 K-1 for natural rubber/graphene nanoplatelet (NR/GNPs) composite and 11.82 Wm-1 K-1 for NR/boron nitride (NR/BN) composite), super conformability(elongation at break ~12%, low hardness and modulus) and excellent electromagnetic interface (EMI) shielding performance (33.96 dB at only 71 um thickness) were fabricated and proved to be superior thermal interface materials for thermal management.