The study of the blood levels of amino acids and carnitine will be able to predict the performance efficiency of young athletes. Objective: to determine blood amino acid concentrations in young athletes and to establish whether they are correlated with the level of carnitine. The study group included 94 athletes with different types of physical activity, as well as children from the control group. The study was conducted by liquid chromatography-tandem mass spectrometry after capillary blood sampling. An analysis of the obtained samples determined the levels of 12 amino acids and identified differences in relation to the type of exercise and gender. The contribution of two amino acids to the variance of the level of bound carnitine was estimated. The contribution of the levels of methionine and phenylalanine was 51.1 and 47.8%, respectively. Thus, the study of the content of amino acids, the level of carnitine, and their relationship can predict the performance efficiency of young athletes, which is especially important to prevent their worse health and lower performance.