Objective To study the effects of umbilical cord-derived mesenchymal stem cells (MSCs) on the growth and metastasis of lung cancer using Lewis lung carcinoma animal models. Methods Animal models of Lewis lung carcinoma were established in 16 C57BL/6 mice and were randomly divided into normal saline (NS) group and MSC group (n=8). Mice in the MSC group were injected with 1×106 MSCs via the tail vein at day 7, 12, and 17. All mice were sacrificed to observe the lung metastases and the tumor size at day 21. Results The average tumor weight was (4.587 5±1.04) g in the NS group and (4.155±1.13) g in the MSC group (P=0.59). The average number of lung metastasis nodules was 3.75±1.39 in the NS group and 1.13±1.13 in the MSC group (P<0.01), showing an inhibitory rate of 70%. Conclusion Umbilical cord-derived MSCs have no effects on the growth of Lewis lung carcinoma in mice, but they can inhibit tumor metastasis.