Methionine (Met.) is amino acid that has proven immune regulatory action. It is usually first limiting amino acid in maize and soybean meal based diet. Met. supplementation in growing chick is a common practice (Swick et al., 1990; Shini & Brydeen, 2005). One of the mechanisms proposed to explain Met. interference in the immune system is the proliferation of T cells, which are sensitive to intracellular glutathione and cysteine levels, compounds also participate in Met. metabolism (Kinscherf et al., 1994). The aim of this study was to investigate the efficacy of Methionine (Met) supplementation on the growth performance and lymphoid organs indices of broiler chickens vaccinated with combined infectious bronchitis (IB)Newcastle disease (ND) vaccines. A total of 120 newly hatched commercial broiler chicks were assigned into four equal treatment groups as follow: First group chicks were vaccinated against IB and ND at 8 and 21 days of age without Met. Second group chicks were vaccinated against IB and ND at 8 and 21 days of age with 0.5% Met. in the diet. Third group chicks remain as control group. Fourth group chicks remain as control group with 0.5% Met. in the diet. Body weight (BW), body weight gain (BWG), feed intake (FI) and lymphoid organs indices were estimated in all groups. Statistical analysis revealed significant (P<0.05) differences among the treatment groups in BW, BWG and better FI as compared with non treatment group. The mean value of thymus, bursa of Fabricius and spleen index of chicks supplemented Met during the period of age showed significant increment (P<0.05). We concluded that better growth performance and lymphoid indices could be obtained with adequate supplementation of Met which have been identified to be in marginal quantities in poultry feed.