An experiment was conducted to investigate amino acid composition of three tropical legumes (Cooper (Glycine wightii), Tinaroo (Neonotonia wightii) and Siratro (Macroptilium atropurpureum)) at two different stages (pre-blooming and blooming stages). Chemical composition and totally 16 amino acids of these plants were analysed for comparison of their composition among species at different growing stages and characterizing the amino acid pattern of these legumes. Crude protein content of the plants ranged from 16% to 27% on a dry matter basis. The total amount of 16 amino acids analyzed in this experiment was highest at 89.7 mg/16 g N in Cooper at pre-blooming and lowest at 80.9 mg/16 g N in Glycine at blooming stage. Total amount of amino acids in each legume species tended to slightly decrease with their maturity but no statistical difference was found. The percentage of aspartic acid, glutamic acid and proline in the total amount of amino acids was dominant at 9% to 13%, and that of methionine was less than 1.6%. In this experiment it was concluded that three tropical legumes were rich in crude protein content and characterized by 16 different amino acids with lower sulfur-containing amino acid as methionine.