Schizophrenia (SCZ) is a severe mental disorder with a multifactorial origin. Distinct biochemical processes that may be involved in SCZ remain unknown; however, some studies have reported the role of amino acids in SCZ. From the hypothesis that an imbalance exists in the level of amino acids in individuals with SCZ compared to that in healthy individuals (HCs), the objective of this work was to identify the 20 proteinogenic amino acids of great biological importance because they are crucial in the involvement of protein synthesis in humans. We then compared the levels of proteinogenic amino acids between individuals with SCZ and HC. Forty-three individuals evaluated according to the criteria defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) was included in this study. Twenty-three patients with chronic SCZ and treated with antipsychotics were matched with twenty HCs by sex and age. Proteinogenic amino acid analysis was based on magnetic resonance metabolomics (1H-NMR). We identified the serum level of 19 major amino acids. The profile showed significant changes in 10 proteinogenic amino acids in the two groups. Cysteine, the only undetected amino acid, is the main precursor of glutathione, and reactive oxygen species that are neurotoxic. Lysine, the most important biomarker identified, metabolizes glutamate via the Pipecolate Pathway, which is predominant in the adult brain. Our results contribute to the understanding of adjacent biochemical processes and reinforces that isolated alterations are insufficient to understand and direct intervention strategies in SCZ thus serving as a source for new testable hypotheses. Keywords: Schizophrenia, proteinogenic amino acids, metabolomic, biomarkers