Polygonum sachalinense F. Schmidt (giant knotweed of Sakhalin knotweed) is a promising species in the Republic of Moldova, which can be used for various purposes, as forage, medicinal, ornamental and edible plant, with high content of vitamins, macro- and microelements, amino acids. 21 amino acids, 7 of which are essential for humans and animals, were found in the dry matter of Sakhalin knotweed. The amount of essential amino acids in leaves was about 10.0 g/kg and, in stems – 40.6 g/kg. The amino acids found in P. sachalinense were: threonine (Thr), valine (Val), isoleucine (Ile), leucine (Leu), phenylalanine (Phe) and lysine (Lys). In stems, leucine was found in higher amounts, as compared with other amino acids; it was followed by lysine and valine. In leaves, the first place, in terms of quantity, was also occupied by leucine, followed by valine and lysine. The amount of proteinogenic amino acids in the mixture of leaves and stems was about 50 g/kg.