Objective: Toxoplasma gondii is a protozoan parasite, which infects Lip to a third of the world's population. Infections are more common and run a more protracted course in patients with Diabetes mellitus (DM). We aimed to determine the prevalence of anti-T. gondii antibodies in patients with type 1 DM. Material and Methods: The study group comprised 85 patients with type 1 DM and 85 healthy volunteers. Micro enzyme-linked ininiunosorbent assay and indirect fluorescent antibody technique were used. Results: T. gondii IgG sero-positivity rate in DM patients (56.62%) was significantly higher than in controls (22.4%). Conclusion: Parasitologic surveys should be repeated periodically in this group of patients.