Single crystalline diamond grains covered by nested carbon nanotubes (CNTs) were constructed using self-assembly techniques. The acid-treated CNTs (MWCNTs-COOH) are first adsorbed onto amine-terminated diamond grains, which were chemically functionalized by silane coupling treatments, in N, N-dimethylformamide solution. Then, the drying and readsorption cycle deposited CNT coatings on the diamond grains due to CNT-CNT interactions caused by van der Waals forces. When the diamond grains were bonded to steel substrates by electroplating using nickel sulfamate plating bath, the bonding strength of the CNT-coated diamond grains to the Ni matrix was almost twice as large as that of the normal diamond grains. Hence, the CNT-coated diamond grains are very useful for improving the tool life of electroplated diamond tools.