Objective: Hashimoto thyroiditis (HT) is among the autoimmune diseases of the thyroid gland. Acute parvovirus B19 infection is suggested to be involved in the pathogenesis of some HT cases. The aim of this study was to test IgM and IgG antibodies against Parvovirus B19 in adult patients with HT. Material and Methods: The study was run in the Department of Internal Medicine, İstanbul University, İstanbul, Turkey between April 2010 and March 2011. Serum samples drawn from 54 adult patients with HT and from 35 age-matched controls were tested for IgM and IgG antibodies against parvovirus B19. The chi-square test and unpaired t-test were used for the comparison between the groups. Results: Anti-parvo virus IgM antibodies were positive in 6 (11.1%) patients and 3 (5.7%) controls while anti-parvo virus IgG antibodies were present in 14 (25.9%) patients and 8 (22.9 %) controls. There was no significant difference between the patient and control groups in terms of antibody positivity (p=0.409, p=0.478). Conclusion: Although the prevalence of antiviral antibodies were higher in patients with HT compared to those in the control group, the difference was not statistically significant. This was attributed to the small number of patients. Nevertheless, this finding may reflect a viral contribution in the pathogenesis of HT.