T-2 toxin is a trichothecene mycotoxin produced by fungi which are known to contaminate cereals, especially in wheat and corn. T-2 toxin is known to cause a range of toxic effects in humans and animals, including immunosuppression and carcinogenesis. Although the effects of T-2 toxin on condition of chickens' spleens have been reported, there has been no systematic study of damage to the spleen of broiler chickens exposed to T-2 toxin. The purpose of the present study was to assess the effects of T-2 toxin on pathology, rates of apoptosis, oxidative stress, and T-lymphocyte subsets in the spleen of broiler chickens. One hundred and twenty male broiler chickens were randomly assigned to one of four groups (30 birds per group), fed 0 mg/kg (control), 0.5 mg/kg, 1 mg/kg, or 2 mg/kg T-2 toxin, respectively. After 21 days, chickens exposed to T-2 toxin demonstrated decreased relative weight and size of the spleen, increased percentage of apoptotic splenocytes, and evident lesions. Concentrations of reactive oxygen species and MDA content increased in splenocytes during T-2 toxin treatments, whereas activities of SOD, CAT, and GSH-PX decreased. The ratio of CD4+/CD8+ T cells also decreased as the dose of T-2 toxin increased. Overall, these results suggest that T-2 toxin causes oxidative stress, leading to increased rates of splenocyte apoptosis and might impair the splenic immune function of broiler chickens.