The electromigration (EM) properties of pure Cu and Cu/carbon nanotube (CNT) composites were studied using the Blech test structure. Pure Cu and Cu/CNT composite segments were subjected to a current density of 1.2 × 106 A/cm2. The average void growth rate of Cu/CNT composite sample was measured to be around four times lower than that of the pure copper sample. The average critical current-density-length threshold products of the pure Cu and Cu/CNT composites were estimated to be 1800 and 5400 A/cm, respectively. The slower EM rate of the Cu/CNT composite stripes is attributed to the presence of CNT, which acts as trapping centers and causes a decrease in the diffusion of EM-induced migrating atoms.