The aim of this study was to determine the acute effect of resistance exercise along with branched chain amino acid (BCAA) supplement on concentration of plasma amino acids, hormonal responses and indices of muscle damage in healthy young women. 10 physically active female students who had at least two sessions of regular exercise per week, and had no history of any supplement consumption, the volunteered to participate in a randomized double blind placebo – controlled cross – over trial. The study design was conducted in two sessions with an interval of six weeks. Resistance protocol included 7 movements (2 lower body and 5 upper body movements) in 5 sets with 12 – 15 repeats and 50% of 1RM. In each session, randomly, half of the subjects received supplement (S) (4.5g BCAA solution) and the other half ingested placebo (P) (same amount of dextrose). Blood samples were collected before the exercise (fasting), immediately, 3 hours and 24 hours after the exercise. These results showed that BCAA supplement drastically increased the BCAA after the exercise (P<0.05). Moreover, in 0 and 3 hours after the exercise, a significant increase in the amount of leucine and isoleucine were observed in supplement condition compared with placebo (P<0.05). However, the methionine in both conditions (S and P) immediately after the exercise reduced (P<0.05) while glutamine and phenylalanine immediately after the exercise significantly reduced only in S condition. In addition, LDH (P>0.05) and CK (P<0.05) increased in both S and P immediately after the exercise. Hormonal changes in insulin and cortisol had a similar pattern in both conditions. It seems that BCAA supplementation only once before acute resistance exercise has a positive effect on plasma BCAA concentrations while the supplement reduced concentrations of glutamine, phenylalanine, and methionine. However, indicators of cell damage (CK, LDH), insulin and cortisol were not affected by pre – exercise BCAA supplementation.