Abstract Recent studies have shown that intestinal commensal bacteria-derived vesicles may have potential effects in alleviating ulcerative colitis (UC). Although Bifidobacterium longum is widely used to prevent colitis, the potential role of B. longum-derived extracellular vesicles has yet to be explored. Here, we extracted B. longum NSP001-derived extracellular vesicles (NEVs) and investigated the regulatory roles of NEVs in colitis.