One hundred and eighty healthy one-day-old broiler chicks were used in this experiment to evaluate the effect of synbiotics and/ or essential oils (EO) as alternatives to antibiotics on performance in induced necrotic enteritis and immunity against vaccination with some common circulating viral diseases. The EO treatment improved the total feed conversion ratio (FCR) in comparison with challenged non-treated group and antibiotic treated group. While using synbiotics did not ameliorate the negative impact of NE challenge on feed intake and FCR. The treatments had positive impact on immune response to vaccination against Newcastle disease (ND), infectious bronchitis (IB), avian influenza (AI) and infectious bursal disease (IBD) as well as they increased the spleen relative weight. The synbiotic treatment alleviate the histopathological changes from vaccination in bursa of Fabricius (BF) as well as antibiotic treated group. The results suggest that EO and synbiotics, as replacements to antibiotics, may be an effective tool to augment performance and immune response of NE challenged birds.