This study was aimed to investigate the effect of dendritic cells (DC) on the proliferation capability, immunophenotype changes, level of secreted cytokines and activity against leukemia of cytokine-induced killer (CIK) cells in vitro. DCs and CIK cells were induced from peripheral blood mononuclear cells of healthy volunteers. They were co-cultured meanwhile CIK cells were cultured alone as controls. Increased number of cells were counted by trypan-blue staining; the killing activity was detected by MTT assay; immunophenotype changes were analyzed by flow cytometry; the IL-12 and INF-gamma levels of the cultured supernatants were detected by ELISA kits. The results showed that the proliferation capability of DC-CIK cells was significantly higher than that of CIK cells (p < 0.05). Under the same condition, the ratio of double positive cells such as CD3(+) CD8(+), CD3(+) CD56(+) in CIK cells was significantly enhanced by co-cultured with DC cells (p < 0.05). The levels of IL-12 and INF-gamma in cultured supernatants of DC-CIK cells increased noticeably on day 3 as compared with CIK cells cultured alone (p < 0.01, p < 0.05). Within the effector-target ratio range between 5:1 to 40:1, the activity of DC-CIK cells against leukemia cells were much higher than that of CIK cells (p < 0.05), and this effect showed a positive correlation with the effector-target ratio. It is concluded that the proliferation capability of DC-CIK cells, the level of their secreted cytokines and their activity against leukemia cells are significantly higher than those of CIK cells. This research may suggest an approach for clinical immunotherapy against leukemia with DC-CIK cells.