To evaluate the effect of dietary supplementation of fat powder and vitamin E- selenium on immune system in transition dairy cows and their calves until weaning day, a total of 32 dairy cows of 21 days before calving were randomly allocated to 4 treatments. Experimental treatments included treatment 1) without fat powder with supplementation of 1500 IU vitamin E and 3.6 mg selenium (equal to recommended NRC level), treatment 2) without fat with supplementation of 3000 IU vitamin E and 7.2 mg selenium (twice recommended level of NRC), 3) 2.5 percent of fat powder with supplementation of 1500 IU vitamin E and 3.6 mg selenium and treatment 4) 2.5 percent of fat powder with supplementation of 3000 IU vitamin E and 7.2 mg selenium. To determine blood parameters in transition dairy cows, they were bled on day 21 before expected parturition and on day parturition. To evaluate blood parameters such as albumin, globulin, total serum protein and immunoglobulin G concentrations in calves, they were bled on birth day and 48 h after birth. Other blood parameters including cholesterol, glucose and TNF-? concentration in calves were measured on birth day and on day 21 after birth. Also, to determine dry matter intake and daily gain weight, they were measured daily and weekly, respectively. Furthermore, rectal temperature and manure score were measured daily. It was observed that experimental treatments did not have any significant effect on blood parameters such as sera globulin, total serum protein, immunoglobulin G and glucose concentrations in transition dairy cows. However, serum albumin concentration tended to decrease (p=0.07) in groups fed fat powder and vitamin E- selenium supplementation. Furthermore, body weight of cows was not affected by supplementation of fat powder and vitamin E- selenium. In addition, applying these supplementations did not affect significantly sera immunoglobulin G and albumin concentrations in calves. Also, administrating fat powder and vitamin E- selenium supplementation could significantly (p 0.001) decrease serum globulin and total serum protein concentrations in their calves. Surprisingly, adding these supplementations led to significantly (p 0.05) increase serum TNF-? concentration in their calves. However, using experimental treatments did not affect sera cholesterol and glucose concentrations in their calves. Although adding these supplementations in diet of dairy cows did not influence feed intake and daily gain weight of their calves, it could improve feed efficiency in their calves. Although, supplementing vitamin E-selenium and fat powder did not significantly affect birth weight, weaning day and weaning weight in their calves, weaning day was decreased. Moreover, manure score and rectal temperature were not affected by adding these treatments. In addition, colostrums compositions including colostrums production, protein percent, lactose percent, total solid not fat, total solid and selenium concentration were not affected by experimental treatments. Fat percent of colostrums was significantly (p 0.01) decreased in groups fed by supplementing of fat powder and vitamin E- selenium (twice recommended level of NRC). Moreover, skeletal growth parameters such as body length, height, hip, pin and were not affected by experimental treatments in their calves. Key words : fat powder, vitamin E, selenium, blood parameter, skeletal growth parameter, colostrum compositions