Purpose: The diagnosis of pediatric autoimmune gastritis (AIG) is critical due to the poor outcome and risk of malignancy. Therefore, we evaluated the prevalence of autoimmune gastritis in children with autoimmune thyroid disease (ATD) and type 1 diabetes mellitus (T1D), using parietal cell antibody (PCA) to identify its use as a screening test. Methods: PCA was measured in 90 patients; 45 patients with ATD (Hashimoto Thyroiditis and Graves' Disease) and 45 patients with T1D. Their ages ranged from 5 to 18 years. Hemoglobin, ferritin, and HbA1c (in diabetic patients) were measured. Results: PCA demonstrated a statistically significant difference between the two groups of patients with a p-value (0.024). The mean value of PCA in patients with T1D was 196.45, while it reached 148.58 in patients with ATD, with a p-value (0.003). Thirty-one (68.9%) and twelve (26.7%) of patients with T1D had high (30-200) and extremely high (> 200) values of PCA, respectively, compared to twenty-six (57.8%) and eight (17.8%) of patients with ATD who had high (30-200) and extremely high (> 200) values of PCA, respectively. Seven (87.5%) of patients with ATD with extremely high PCA( above 200) also had normocytic anemia.