The efficiency of a commercial probiotic (Pronifer) as a feed additive on the performance and immunological status of the broiler chicks (Arbor acre) has been investigated. As there is no model currently available which will predict the use of pronifer under practical normal conditions, the product was added at a level of 1Kg/ton diet in an attempt to compare its addition to control one (groups I & II ).In addition pronifer was added at 1Kg & 2Kg/ton diet to groups (III & IV) when wheat bran was replacing 5% of the basal diet. The addition of the pronifer to the basal diet improves the body weight by (3.44%) than the control group. Its effect appeared clearly when added to the diets containing wheat bran with the superiority of the high level (2Kg/ton diet) of supplementation (6.12%) and recorded good for feed conversion (2.2) in comparison with the control group.Pronifer tratment drastically reduced the total viable bacterial count total coliform, Escherichia coli with disappearance of Clostridium perfringes after 2 weeks of treatment. The immuno pathological examination of the spleen revealed hyperplasia of the white pulp with the presence of neumorus prolymphocytic cell proliferation. There was also increase in the number of alkaline phosphatase activated B-lymphocyte in the splenic red pulp. The bursa in the pronifer treated group showed increase in the number of the follicles with presence of neumorus plasma cell reaction in the medulla. The haematological picture showed increase in the number of total erythrocytic and leucocytic cell count with marked increase in the percentage of lymphocyte and monocyte. It was inferred from the present study that the pronifer has brought about benificial effects in the performance and immunological status of broilers and was cost effective.