Obesity is prevalent worldwide and is associated with the development of insulin resistance and type 2 diabetes. Obesity-induced chronic low-grade inflammation has been suggested to be an important mechanism for the development of IR. Adipose tissue is a key organ for this chronic inflammatory response. Increased accumulation of adipose tissue macrophages (ATMs) has been demonstrated in obese rodents and humans by numerous studies. It is now well established that ATMs are the primary source of inflammatory cytokine production in adipose tissue and play a key role in obesity-induced chronic low-grade inflammation and IR. Although there have been some advances in the study of ATMs in obese conditions, the mechanisms underlying ATMs recruitment and activation remain to be determined.