Abstract: To clarify the influence of acute stress on plasma amino acid concentrations, chicks were exposed to either restraint with isolation stress or fasting stress. In restraint with isolation-induced stress, plasma L-hydroxyproline, L-serine, L-asparagine, β-alanine, L-alanine, L-histidine, L-arginine, L-proline, L-methionine, L-leucine, L-phenylalanine and L-ornithine decreased compared with the control. During fasting stress, L-asparagine, β-alanine, L-histidine, GABA, L-threonine, L-arginine, L-proline, L-methionine, L-leucine, L-phenylalanine and L-ornithine linearly decreased while, tryptophan increased. Most of the amino acids modified in both acute stresses have been recognized to have a role in sedation and/or hypnosis. Amino acids quickly metabolized during acute stress should be supplemented before and/or after stressful conditions to support chicken health.