To investigate the effect of berberine on brown adipose tissue(BAT) activation in Zucker diabetic fatty(ZDF) rats and explore its potential underlying mechanism.Methods:Forty spontaneously obese type 2 diabetic ZDF(fa/fa) rats were randomly divided into five groups using a random number table based on body weight and random blood glucose levels：model group，metformin hydrochloride group，high-dose berberine group，medium-dose berberine group，and low-dose berberine group，with 8 rats in each group.Eight age-matched，lean，healthy spontaneously obese Zucker(fa/+) rats served as the normal control group.All groups received oral gavage treatment for 8 consecutive weeks.Blood glucose and body weight were measured.The ratios of white adipose tissue(WAT) and BAT were calculated.Adipose tissue morphology was observed，and the mRNA expression of peroxisome proliferator-activated receptor gamma coactivator-1 alpha(PGC-1α) in BAT was detected.Protein expression levels of uncoupling protein-1(UCP-1)，PR domain-containing 16(PRDM16)，and peroxisome proliferator-activated receptor gamma(PPARγ) were determined using Western blot.Results:Compared with the model group，the metformin group and the high-and medium-dose berberine groups showed significant differences in controlling body weight gain and reducing blood glucose levels(P<0.05，P<0.01).The BAT/WAT ratio was significantly decreased in the metformin group and all berberine-treated groups(P<0.01).Adipocyte diameter was significantly reduced in the metformin group，and relatively reduced in all berberine groups，with the effect most pronounced in the high-dose berberine group.Compared with the model group，the protein expression levels in the metformin and high-and medium-dose berberine groups were significantly upregulated(P<0.01).Similarly，mRNA expression in the metformin，high-dose，and medium-dose berberine groups was significantly increased(P<0.05，P<0.01).Conclusion:Berberine can reduce blood glucose levels and body weight in model rats，and it promotes BAT activation in obese type 2 diabetic ZDF rats，potentially through upregulation of proteins and mRNA expression associated with the PPARγ/PGC-1α signaling pathway.