AbstractThe human microbiome significantly influences drug metabolism through the gut–liver axis, leading to modified drug responses and potential toxicity. Due to the complex nature of the human gut environment, the understanding of microbiome‐driven impacts on these processes is limited. To address this, a multiorgan‐on‐a‐chip (MOoC) platform that combines the human microbial‐crosstalk (HuMiX) gut‐on‐chip (GoC) and the Dynamic42 liver‐on‐chip (LoC), mimicking the bidirectional interconnection between the gut and liver known as the gut–liver axis, is introduced. This platform supports the viability and functionality of intestinal and liver cells. In a proof‐of‐concept study, the metabolism of irinotecan, a widely used colorectal cancer drug, is imitated within the MOoC. Utilizing liquid chromatography coupled to tandem mass spectrometry (LC‐MS/MS), irinotecan metabolites are tracked, confirming the platform's ability to represent drug metabolism along the gut–liver axis. Further, using the authors’ gut–liver platform, it is shown that the colorectal cancer‐associated gut bacterium, Escherichia coli, modifies irinotecan metabolism through the transformation of its inactive metabolite SN‐38G into its toxic metabolite SN‐38. This platform serves as a robust tool for investigating the intricate interplay between gut microbes and pharmaceuticals, offering a representative alternative to animal models and providing novel drug development strategies.