Abstract: Obesity is an escalating global pandemic posing a serious threat to human health. The intervention therapy using weight-reducing drugs, accompanied by lifestyle modification, is a strategy for the treatment of obesity. In the present study, we explored the role of fucoidan, a seaweed compound, on high-fat diet (HFD)-induced obesity in mice. We found that fucoidan treatment significantly reduced the body fat and caused redistribution of visceral and subcutaneous fat in HFD-fed mice. Meanwhile, fucoidan treatment inhibited adipocyte hypertrophy and inflammation in adipose tissue. Collectively, these results suggest that fucoidan may be a promising treatment for obesity and obesity-induced complications.