Background <p>Inborn errors of immunity (IEIs) are defined by impaired immune function and abnormal immune system development. The recognition of significant interactions between the immune and endocrine systems has emerged as an area of growing clinical interest. The study aimed to evaluate the frequency of thyroid nodules and autoimmune thyroid diseases in patients with IEIs.</p> Materials and methods <p>This study included 40 IEI patients and 65 healthy subjects as control group. Demographic and clinical data were collected from medical records. All participants underwent thyroid ultrasound and biochemical evaluation for thyroid function tests and autoantibody levels. The diagnosis of autoimmune thyroid disease (AITD) diagnosis was based on thyroid specific autoantibody levels, thyroid function tests, and/or ultrasonographic features consistent with thyroiditis.</p> Results <p>Thyroid nodules were detected in 5 patients (12.5%) in the IEI group and in 14 subjects (21.5%) in the control group, with no statistically significant difference in thyroid nodule frequency between the two groups (<i>p</i> = 0.243). AITD was significantly more prevalent in the IEI group compared to controls (45.0% vs. 23.1%; <i>p</i> = 0.019). Mean total thyroid volume was significantly smaller in IEI patients than in controls (6.85 ± 2.92 mL vs. 10.52 ± 5.44 mL; <i>p</i> &lt; 0.05).</p> Conclusions <p>Our findings demonstrated that AITD is significantly more prevalent in IEI patients. Thyroid nodule frequency did not differ between groups. These findings support the routine incorporation of thyroid ultrasonography and autoantibody screening into IEI follow-up protocols. Larger multicenter prospective studies are warranted to confirm these observations across diverse IEI subtypes.</p>