Control of gut microbes is crucial for not only local defense in the intestine but also proper systemic immune responses. Although intestinal epithelial cells (IECs) play important roles in control of enterobacteria, the mode of the involvement is not fully understood. We generated mice harboring IEC-specific deletion of IkappaB-zeta nuclear NF-kappaB-regulatory protein, and investigated the effect on the bacterial flora in the gastrointestinal tract. We sequenced the V4 region of the bacterial 16S rRNA gene of the DNA samples from the small intestine and feces. Deletion of IkappaB-zeta in IECs resulted in dysregulation of microbiota especially with marked expansion of segmented filamentous bacteria (SFB), culminating in enhanced Th17 cell development and exacerbation of inflammatory diseases. The dysregulation of the microbiota is due to impaired expression of a set of anti-microbial genes in the mutant mice. Thus, IkappaB-zeta controls qualification of intestinal microbiota in IECs.