Cadmium (Cd), a potent immunotoxicant, has been reported to affect immunocytes both in humans and in rodents. However, whether such an effect exists in birds is still unclear. To delineate the cytotoxicity of Cd on the bird immunocytes in vitro, chicken splenic lymphocytes were exposed to Cd. A significant increase in the occurrence of cell damage was observed in chicken splenic lymphocytes following Cd administration. The enhanced level of LPO and the overproduction of ROS suggested that Cd caused oxidative stress in chicken splenic lymphocytes. A pronounced inhibition of SOD and GPx was seen after being indicated with 10 μM Cd for 36h or indicated with 15 μM Cd for 24 h. In addition, DNA damage and apoptosis was observed in chicken splenic lymphocytes treated with Cd. The degree of DNA damage and the number of apoptotic cells rose in a time- and dose-dependent manner. These results clearly demonstrate that chicken splenic lymphocytes appear to be more susceptible than mammalian immunocytes to the adverse effects of Cd. The oxidative stress and subsequent DNA damage and apoptosis induced by Cd are important mechanisms of Cd cytotoxicity to bird immunocytes.