Tobacco smoking favorably influences the course of Hashimoto thyroiditis, possibly through the antiinflammatory proprieties of nicotine. In this study we tested anatabine, another tobacco alkaloid, in a model of experimental autoimmune thyroiditis. Experimental autoimmune thyroiditis was induced by different doses of thyroglobulin, to produce a disease of low, moderate, or high severity, in 88 CBA/J female mice: 43 drank anatabine supplemented water and 45 regular water. Mice were bled after immunization and killed to assess thyroid histopathology, thyroglobulin antibodies, T₄, and thyroid RNA expression of 84 inflammatory genes. We also stimulated in vitro a macrophage cell line with interferon-γ or lipopolysaccharide plus or minus anatabine to quantitate inducible nitric oxide synthase and cyclooxygenase 2 protein expression. Anatabine reduced the incidence and severity of thyroiditis in the moderate disease category: only 13 of 21 mice (62%) developed thyroid infiltrates when drinking anatabine as compared with 22 of 23 (96%) controls (relative risk 0.59, P = 0.0174). The median thyroiditis severity was 0.5 and 2.0 in anatabine and controls, respectively (P = 0.0007 by Wilcoxon rank sum test). Anatabine also reduced the antibody response to thyroglobulin on d 14 (P = 0.029) and d 21 (P = 0.045) after immunization and improved the recovery of thyroid function on d 21 (P = 0.049). In the thyroid transcriptome, anatabine restored expression of IL-18 and IL-1 receptor type 2 to preimmunization levels. Finally, anatabine suppressed in a dose-dependent manner macrophage production of inducible nitric oxide synthase and cyclooxygenase 2. Anatabine ameliorates disease in a model of autoimmune thyroiditis, making the delineation of its mechanisms of action and potential clinical utility worthwhile.