The tryptophan-kynurenine metabolism is the primarily metabolic pathway of the essential amino acid tryptophan degradation and is involved in various physiologic and pathophysiologic mechanisms. Acute (single) and chronic (multiple) bouts of physical exercise impact the tryptophan-kynurenine metabolism in different populations. While effects of chronic intervention studies have been scarcely observed, acute exercise in terms of incremental exercise tests until exhaustion show robust effects, especially concerning an activation and an increased metabolic flux towards kynurenic acid as end product. The present work aims to investigate whether different exercise modalities provoke different acute effects on the tryptophan-kynurenine metabolism in young healthy males. Aerobic exercise modalities, in particular, but also hypertrophic strength loads seem to augment the metabolic flux towards kynurenic acid. Since kynurenic acid is an endogenous ligand of the aryl-hydrocarbon-receptor, the increase measured in blood serum suggests a systemically greater ligand availability of the aryl- hydrocarbon-receptor. Due to its immunosuppressive properties, an activation of the aryl-hydrocarbon-receptor may represent an important link between exercise-induced acute effects and longer-term adaptions of the immune system. Future studies are needed to confirm the present findings in other samples (e.g., women, older people) and clinical populations. Targeted chronic exercise interventions that may have the potential to normalize a deregulated tryptophan-kynurenine-metabolism in different chronic diseases can be designed based on the present results.