Polymer-based shielding materials have garnered attention due to their lightweightness, ease of fabrication, and tailorable performance. However, they tend to creep and deform when the materials are exposed to external heat, which may cause a catastrophic disaster due to mechanical failure. In this study, a hybrid loading of graphite (Gt) and boron nitride (BN) fillers was used to improve the thermal dissipation, neutron shielding, and tribological properties of ultrahigh molecular weight polyethylene (UHMWPE), which demonstrate potential applications in nuclear sectors among others. The results revealed that the thermal conductivity of UHMWPE/BN 30 wt %/Gt 40 wt % composite (i.e., BN30Gt40) reached as high as 8.43 W/mK, which was 295% higher than UHMWPE/BN 30 wt %, 201% higher than UHMWPE/Gt 40 wt %, and 1700% higher than pure UHMWPE, respectively. Simulation analysis using Geant4 suggested that UHMWPE/BN/Gt composites exhibited excellent neutron-shielding performance due to the presence of abundant hydrogen and boron elements. In addition, the composites demonstrated excellent friction and wear performance due to the combined effects of constructing transfer film on the surface of the friction pair and timely removal of frictional heat that was generated at the sliding interface.