Irritable bowel syndrome (IBS) is a common chronic gastrointestinal disorder, with diarrhea-predominant IBS (IBS-D) as the most frequent subtype. The implication of gut microbiota in the disease's etiology is not fully understood. In vitro gut systems can offer a great alternative to in vivo assays in preclinical studies, but no model reproducing IBS-related dysbiotic microbiota has been developed. Thanks to a large literature review, a new Mucosal ARtifical COLon (M-ARCOL) adapted to IBS-D physicochemical and nutritional conditions was set-up. To validate the model and further exploit its potential in a mechanistic study, in vitro fermentations were performed using bioreactors inoculated with stools from healthy individuals (n = 4) or IBS-D patients (n = 4), when the M-ARCOL was set-up under healthy or IBS-D conditions. Setting IBS-D parameters in M-ARCOL inoculated with IBS-D stools maintained the key microbial features associated to the disease in vivo, validating the new system. In particular, compared to the healthy control, the IBS-D model was characterized by a decreased bacterial diversity, together with a lower abundance of Rikenellaceae and Prevotellaceae, but a higher level of Proteobacteria and Akkermansiaceae. Of interest, applying IBS-D parameters to healthy stools was not sufficient to trigger IBS-D dysbiosis and applying healthy parameters to IBS-D stools was not enough to restore microbial balance. This validated IBS-D colonic model can be used as a robust in vitro platform for studies focusing on gut microbes in the absence of the host, as well as for testing food and microbiota-related interventions aimed at personalized restoration of gut microbiota eubiosis.