The aim of this work is to demonstrate a facile and scalable method to produce carbon nanosheet (CNS) based composites. CNSs and copper composite powders were produced directly from graphite and copper particles in liquids using a high shear rotor–stator mixer, the method is called particle-assisted shear exfoliation (PASE). CNS reinforced copper composites were produced with the composite powders by spark plasma sintering (SPS). High strengthening efficiencies of CNSs in copper matrix composites were found, which are similar to those of carbon nanotubes. The interfacial microstructure of the composites was studied; a close contact between carbon and copper was obtained in the composite, which contributes to the mechanical property of the composites. PASE is also promising to produce many other kinds of composites by choosing numerous other layered crystals and nanomaterial particles.