Our study showed that Hsp–Cu(II) increased the abundances of Bacteroidota and Faecalibaculum in the T2DM mice, and the levels of DAO and D-LAC in the Hsp–Cu(II) groups were lower than those in the Diseased group, indicating that Hsp–Cu(II) significantly decreased intestinal permeability and improved the intestinal mucosal barrier function to alleviate T2DM. Here, HSP90B2P is linked to type 2 diabetes mellitus.