Abstract Adipocyte-macrophage crosstalk plays a critical role to regulate adipose tissue microenvironment and cause chronic inflammation in the pathogenesis of obesity. Interleukin-29 (IL-29), a member of type 3 interferon family, plays a role in host defenses against microbes, however, little is known about its role in metabolic disorders. We explored the function of IL-29 in the pathogenesis of obesity-induced inflammation and insulin resistance. We found that serum IL-29 level was significantly higher in obese patients. IL-29 upregulated IL-1β, IL-8, and monocyte chemoattractant protein-1 (MCP-1) expression and decreased glucose uptake and insulin sensitivity in human Simpson-Golabi-Behmel syndrome (SGBS) adipocytes through reducing glucose transporter 4 (GLUT4) and AKT signals. In addition, IL-29 promoted monocyte/macrophage migration. Inhibition of IL-29 could reduce inflammatory cytokine production in macrophage-adipocyte coculture system, which mimic an obese microenvironment. In vivo, IL-29 reduced insulin sensitivity and increased the number of peritoneal macrophages in high-fat diet (HFD)-induced obese mice. IL-29 increased M1/M2 macrophage ratio and enhanced MCP-1 expression in adipose tissues of HFD mice. Therefore, we have identified a critical role of IL-29 in obesity-induced inflammation and insulin resistance, and we conclude that IL-29 may be a novel candidate target for treating obesity and insulin resistance in patients with metabolic disorders.