The association of different infections with the subsequent occurrence of autoimmunity, just like autoimmune thyroiditis, has recently been increased globally. This study aimed to determine the role of Helicobacter pylori (HP) infection in Hashimoto's disease. The research groups involved 50 patients with Hashimoto's disease and 50 healthy subjects. All of them were subjected to the estimation of concentrations of free triiodothyronine (FT3), free thyroxine (FT4), TSH, antithyroid peroxidase (anti-TPO), and anti-thyroglobulin (anti-Tg). In addition, for the diagnosis of HP, IgG, as well as anti-CagA antibodies in the serum, were detected. An independent t-test was used to test the significance of the means. Also, an odd ratio was used to clarify the association between H. pylori infection and HT disease. Statistical significance was detected when P-value is equal to or less than 0.05. The results indicated that 94% of Hashimoto's patients and 34% of the healthy subjects were seropositive for HP IgG. Also, (74%) of the HT patients were seropositive for HP IgG/anti-CagA. These results were significant at the level of 0.01 (p< 0.001). Hashimoto's patients with HP/CagA positive tests have significantly elevated concentrations of anti-TPO (480.69±311.29), anti-Tg (336.00±175.95), and TSH (20.43±18.98) compared with patients tested negatively to HP/CagA antibodies (358.60±281.55, 258.36±170.09 and 9.02±5.94 respectively). In conclusion, there is a relationship between H. pylori infection and the development of Hashimotoʼs thyroiditis in Iraqi patients. H. pylori infection, especially CagA expressing strains, could be a risk factor for the development of autoimmune hypothyroidism and to a lesser extent its progression by increasing the concentration of thyroid antibodies and TSH, which in turn leads to decreased levels of the thyroid hormones and worsening of the disease, requesting antibiotic therapy to eradicate the bacterial infection.