The overheating of microelectronic components has become a critical problem for electronic industry and it leads to structural failure of the electronic devices. The development of heat sink materials with enhanced thermal conductivity can solve thermal problem by dissipating the heat. The thermal conductivity of the carbon nanotubes (CNTs) ranges between 1200-3000 W/m.K are the best candidate for the development of heat sink material. This research investigates the effects of reinforcing CNTs on the thermal conductivity of copper matrix composites. Mixtures of copper powder and CNTs were prepared and pressed under compacting pressure of 580 MPa. The compacted samples were sintered in the inert atmosphere at 900°C. Sintered density of copper composites was measured and compared with theoretical density calculated using Rule of Mixtures (ROM). The results showed 96-98 sintered density was achieved. Optical and scanning electron microscopic (SEM) examination of sintered compacts showed good grain growth that resulted in approximately 1 increase in dimensions of specimen. However, in few samples, porosity was also noted. Field emission scanning electron microscopic (FESEM) study showed well dispersion of CNTs in copper matrix and interfacial bonding between copper particle and CNTs. In this experiment, the addition of 2V/o of CNTs in copper resulted in 9 increase in the thermal conductivity of sintered copper.© 2008 Metal Powder Industries Federation.