Abstract: In order to evaluate using herbal methionine instead of synthetic methionine in feed for broiler chickens and its influence on performance indicators, carcass yield and production cost, an experiment was conducted with 500 Ross broiler chicks within 40 days. The birds were classified in 5 groups including lack of methionine dietary (control), diets containing 0.1 and 0.2% of herbal methionine, 4 repeats and each repetition 25 birds were selected randomly. At the end of starter, grower and finisher periods, indexes of weight gain, feed intake and feed conversion ratio have been investigated. Moreover, 2 birds of each iteration of the carcass in the main parts were tested in the fortieth day after weighing and slaughter. The cost of production and profit from each feeding group were also assessed with the numerical calculations at the end of each period. The results showed that herbal methionine has been ineffective or reducing significantly for the indexes of weight gain and feed intake in all periods. On the contrary, the level of synthetic methionine causes increase of weight and increase or equality in average feed consumption. In feed conversion ratio index, levels of herbal methionine have been identical or increasing in comparison with control group. In all periods, synthetic methionine has increased the indexes. Chicken breast weight did not change with different herbal methionine. This behavior was observed in synthetic methionine but synthetic methionine increases breast weight significantly in comparison to herbal methionine. Abdominal fat has also been reduced by both methionine source but this reduction was more in herbal methionine (p<0.01). The weight ratio of liver reduced for both methionine sources (identically) in comparison to control group. The results of studying production costs indicate that none of the herbal methionine consumption levels has the economic justification and the positive profit balance in comparison to synthetic methionine. This balance was even lower than the group lacking methionine. Accordingly, substitution of herbal methionine with synthetic methionine is not proper in fodder for broiler chickens.