Graphene film (GF) is widely used for heat dissipation in portable electronic devices by virtue of its lightweight and high thermal conductivity (K). However, in practical applications, mold-cutting GF inevitably generates plenty of scraps with high K, so it is worthwhile to investigate the secondary utilization of scraps. This contribution first used polydopamine (PDA) to surface-modify the crushed large-sized graphite nanosheets (GNs) powder scraps to obtain GNs@PDA. Then the GNs@PDA was mixed with graphene oxide (GO) sheets to prepare graphene/GNs@PDA (G/PG) composite films via self-assembly. After graphitization, the graphitized PDA “welded” the GNs to the derived graphene through covalent bonds. The resulting long-range ordered defect-free lamellar stacking structures effectively facilitated the transfer of phonons and electrons, thus significantly enhancing the K and electrical conductivity of the G/PG film. The in-plane K and electrical conductivity of the G/PG film are up to 1301.8 W/mK and 5939.0 S/cm, respectively. Furthermore, G/PG films also exhibit superior mechanical properties, foldability, and electromagnetic shielding performance. This work provides ideas for the preparation of flexible heat spreaders and realizes the reuse of GF scraps.