The study presented here aimed to investigate possible dietary arginine (Arg) by methionine (Met) interaction in broiler chicks. A total of 540 day-old Ross 308 broiler chicks were randomly assigned into the 9 experimental diets with 5 replicates of 12 birds each. Dietary treatments consisted of a 3×3 factorial arrangement with three dietary Arg levels (90, 100 or 110% of NRC specifications for Arg) and three Met levels (90, 100 or 110% of NRC recommendations for dietary Met content), which fed during a 42 d feeding trial. Average daily feed intake (ADFI) and gain (ADG) as well as feed conversion ratio (FCR) were recorded periodically as starter (1-21 d of age) and grower (21-42 d of age) periods. At the final trial day, two birds per each pen were slaughtered to evaluate carcass measurements. Also, antibody production titers against viral antigens and sheep red blood cell (SRBC) were measured after respective antigen inoculations. Furthermore blood biochemical parameters were measured at d 21 and 42 of age. Results showed that body weight gain was increased (P 0.01) during starter, grower and entire trial periods by both dietary supplementation of Arg and Met up to 100% of NRC recommendations. Feed conversion values during all trial periods were decreased (P 0.01) as the result of incremental Met levels, but the highest difference was obtained by Met supplementation up to 100% of NRC recommendations. Furthermore, Arg fortification of deficient-diets improved (P 0.05) FCR values during all experimental stages. The significant Arg by Met interactions were observed for FCR values during weeks 1 and 4 so that, Met fortification of diets was more effective when diets already supplemented with Arg level of 110% of NRC recommended values. Incremental Arg levels up to 110% of NRC values increased (P 0.01) relative weight of bursa of Fabricius and Met supplementation (110%) had conversed effect on bursa weight in diets contain in 90 and even 100% Arg. Dietary Met supplementation up to 100% of NRC Specifications increased (P 0.05) antibody titer against SRBC injection. Also, incremental levels of methionine (P=0.0712) up to 100% and arginine (P=0.0991) up to 110% of NRC tended to increase antibody responses against Newcastle disease virus (NDV). In addition, Arg fortification of dietenhanced (P 0.01) antibody titer against bronchitis virus (IBV), whereas Met supplementation tended (P=0.0760) to increase anti-bronchitis titers. On the other hand, both Met and Arg up to 100% of NRC values increased (P 0.01) antibody response against infection bursal disease (IBD) virus. The significant Arg×Met interactions were observed for antibody titers against SRBC, IBV and IBD so that, Arg fortification of diets up to 110% of NRC was more effective when diets already supplemented with Met level of 100% of NRC. Incremental levels of Met and Arg up to 110 and 100% of NRC, respectively, enhanced serum gammaglobulins. At d 21, Met level up to 110% of NRC recommendations tended (P=0.09) to decrease serum high-density lipoproteins (HDL) and Arg×Met interaction affected (P 0.05) HDL values. Arginine level up to 110% of NRC specifications increased low-density lipoproteins. Dietary Arginine supplementation increased (P 0.05) serum HDL concentration at d 42 of age. One could achieve maximum performance and feed efficiency with supplementation of diets with Arg and Met up to 110 and 100% of NRC recommendations, respectively. The present findings confirm dietary Arg×Met interaction to promote immunological responses of broiler chicks Keywords: Broiler Chicks, Arginine, Methionine, Blood Biochemistry, Growth Performance, Antibody Titer, Cellular and Humoral Immune Response Carcass Characteristics