Disulfiram is a drug used to treat alcohol dependence. Recent studies have shown that disulfiram also has anti-cancer effects. Considering that many anti-cancer agents have side effects, including immunosuppression, it is important to check if disulfiram has some cytotoxicity to immune cells. In this study, mouse spleen cells were treated with disulfiram and the metabolic activity was measured. Disulfiram increased the cell death of spleen cells according to annexin V-FITC/PI staining analysis. In addition, disulfiram decreased the mitochondrial membrane potential of spleen cells. The toxicity of disulfiram was concentration dependent. Interestingly, disulfiram affected the population of lymphocytes and the subset of spleen cells was altered. This study provides clinicians and researchers with valuable information regarding the toxicity of disulfiram to mouse spleen cells, particularly lymphocytes.