Puerarin has been suggested to improve ruminant productivity, but its effects on rumen fermentation and rumen microbiota in sheep remain insufficiently understood. In this study, Hu sheep were fed diets supplemented with 0, 50, 100, 200, 400, or 800 mg/kg puerarin for 30 d to evaluate growth performance, apparent nutrient digestibility, serum biochemical and antioxidant indices, rumen fermentation, and rumen microbial community structure. Puerarin supplementation improved growth performance, with the 100 mg/kg group showing the greatest average daily gain. Acid detergent fiber digestibility was also significantly increased in the 100 mg/kg group. In the rumen, microbial crude protein concentration was significantly increased in the 100 and 400 mg/kg groups, propionate concentration was significantly increased in the 50 and 100 mg/kg groups, and the acetate-to-propionate ratio was significantly decreased in the 100 mg/kg group. In serum, albumin and glucose concentrations were significantly increased at appropriate supplementation levels, whereas malondialdehyde was reduced in the 100 mg/kg group but increased in the 800 mg/kg group. 16S rRNA sequencing showed limited effects on overall bacterial diversity, but changes in specific rumen microbial taxa and predicted microbial functions were observed. Collectively, these findings suggest that dietary puerarin, particularly at 100 mg/kg, may improve growth performance in Hu sheep, at least in part, through improving rumen fermentation.