Xanthoceras sorbifolium Bunge leaves (XBL), traditionally consumed as herbal tea, have attracted increasing attention as potential functional food ingredients for managing type 2 diabetes mellitus (T2DM). This study investigated the anti-diabetic effects of an aqueous XBL extract in T2DM rats induced with a high-fat, high-sucrose diet combined with streptozotocin. XBL administration significantly improved glycemic control, insulin sensitivity, lipid profiles, and pancreatic and renal histopathology. Integrated 16S rRNA sequencing and untargeted fecal metabolomics revealed the modulation of key metabolic pathways, including linoleic acid and histidine metabolism, and elevated production of short-chain fatty acids (SCFAs) such as acetate and propionate. XBL also enriched beneficial gut microbes including Prevotella, Lachnospiraceae_NK4A136_group, and [Eubacterium]_xylanophilum_group, whose abundance showed positive correlations with SCFA levels and metabolic improvements. These findings demonstrate that XBL ameliorates T2DM through gut microbiota–SCFA–metabolite interactions and suggest its potential as a natural, multi-target dietary strategy for metabolic health management.