Functional oligosaccharides have attracted attention as dietary interventions for type 2 diabetes mellitus (T2DM). However, the effects of oligosaccharides derived from Dendrobium officinale (DOO1) in T2DM remain unclear. This study evaluated the effects of DOO1 on metabolic parameters, gut microbiota, short-chain fatty acids (SCFAs) production, intestinal barrier function, and host metabolism in db/db mice. DOO1 significantly improved glucose and lipid metabolic disorders and reduced pancreatic and hepatic injury. These effects were accompanied by changes in gut microbiota composition, characterized by increased abundances of Duncaniella, Muribaculum, and Paramuribaculum, along with elevated fecal SCFA levels. DOO1 improved intestinal barrier function, as indicated by reduced intestinal permeability and inflammatory markers (TNF-α, IL-1β, LPS), and increased expression of Muc2, ZO-1, and Claudin-1. DOO1 also altered host metabolic profiles and regulated gut-derived hormones and appetite-related neuropeptides. Overall, these findings suggest that DOO1 may alleviate T2DM-related metabolic disorders by modulating gut microbiota and host metabolism.