Probiotics are live bacteria that could exert health beneficial effects; however, their immunological effects in sheep are still scarce. The aim of this study was to investigate the immunomodulatory role of probiotics in 12 rams weighing 30–35 kg. The animals were divided into 2 groups (6 animals each), one group served as a control and the other as a probiotic treated one. Treated rams were given orally commercial probiotic strains (Sacharomyces cerevisiae, Lactobacillus acidophilus, Lactobacillus plantarum and Enterococcus faecalis) mixture in a dose of 10 g/head/day for one month. Blood samples were collected from control and treated rams at the end of the whole experimental period. Total and differential leukocyte counts (TLC and DLC), interleukin 10 (IL-10) and 12 (IL-12) serum concentration, IL-10/IL-12 ratio, lymphocyte transformation and DNA damage (comet assay) were determined. TLC in the blood of treated rams decreased significantly (P = 0.009), the serum levels of IL-10 and IL-12 were not significantly changed, while IL-10/IL-12 ratio was significantly (P = 0.03) increased after probiotic mixture administration in rams. The administration of probiotic mixture significantly (P = 0.0001) enhanced the transformation of lymphocytes in rams’ blood. After probiotic mixture administration, the percent of DNA in the comet tail declined significantly (P = 0.02) from 2.75% to 2.57%. The present study demonstrated that leukocytes, cytokine production, lymphocyte transformation and DNA integrity were differentially influenced by the tested probiotic strains mixture. The biological importance of specific effects of probiotics in sheep remains to be determined.