BACKGROUND: Although probiotics-based therapies and postbiotics derived from Lactobacillus reuteri (L. reuteri) hold promising potential in mitigating alcohol-associated liver disease (ALD), the role of L. reuteri's metabolite, 3-Hydroxypropionaldehyde (3-HPA, reuterin), remains elusive. PURPOSE: The objective of this study is to examine the influence of 3-HPA on the attenuation of alcohol-induced hepatic steatosis and its underlying mechanisms. METHODS: The study utilizes network pharmacology to identify potential targets for 3-HPA in treating ALD. Comprehensive analytical methods, including histological and biochemical assessments, coupled with metabolomics techniques, are employed to evaluate the protective mechanisms and actions of 3-HPA in ALD. Additionally, the therapeutic potential of hepatic aryl hydrocarbon receptor (AhR) activation is explored through using both an AhR agonist and inhibitor, in order to assess the potential of 3-HPA as an AhR ligand in treating ALD. RESULTS: Chronic alcohol consumption stimulates AhR activation in hepatocytes, both in vivo and in vitro, leading to the disruption of hepatic tryptophan metabolism. Our observations indicate that 3-HPA has the potential to regulate this process by activating AhR signaling through modulating tryptophan metabolism, specifically affecting indole acetaldehyde, indole, and 5‑hydroxy-l-tryptophan (5-HTP) levels. Mechanistically, 3-HPA demonstrates potential as an effective AhR agonist in mitigating ethanol-induced liver injury by regulating AhR-CD36 signaling, thereby exerting protective effects against hepatic steatosis. CONCLUSION: Ultimately, the study identifies a previously uncharacterized role of 3-HPA in alleviating alcohol-associated liver injury and hepatic steatosis. It further elucidates that 3-HPA serves as a mediator in tryptophan metabolism, activating the AhR signaling, thereby suggesting its potential as a promising candidate for the treatment of ALD.