Background: Immune thrombocytopenia (ITP) is an immune-mediated hematologic disorder in which increased platelet destruction and decreased platelet production lead to thrombocytopenia and, thus, mucocutaneous bleeding. The interleukin-1 (IL-1) family is involved in many human diseases by regulating innate immunity and inflammation. As a new IL-1 family member found in 2005, IL-33 and its receptor play important roles in inflammation, cancer, allergy and autoimmune diseases and are potential therapeutic targets. The aim of this work was to evaluate IL-33 among active ITP patients and remission in relation to control. Methods: This is a case control study This study was conducted in the Outpatient Clinic of Hematology Unit of Pediatric Department and Clinical Pathology Department at Zagazig university hospitals during the period from October 2017 to April 2018, on Twenty two ITP Patients during their regular follow-up visits and Twenty two age and sex-matched healthy children as a control group. Forty four subjects were included in this study; they were classified into two groups as follow: Control group and Patient group: Each group was subjected to the following: History, examination and Laboratory workup including IL-33.Results: There was no statistically significant difference between cases and control regarding sex and age.Purpura, ecchymosis and mucous membrane bleeding (90.9%,81.81% and72.7% respectively) were the most common clinical data among ITP cases group. Less common splenomegaly and lymphadenopathy were (4.54% and .0%) respectively. There was no statistically significant difference between cases and control regarding HB, RBCs, WBCs and lymphocytes %.Mean value of Platelets was significantly lower among cases than controls (28.14, 288.64 respectively) P=.000.Mean value of IL-33 was significantly lower among cases than controls (24.68, 47.18 respectively) P=.000.There was statistically significant difference between acute ITP patients and chronic ITP patients regarding IL-33 (P value=.000).There was statistically significant difference between acute ITP patients and controls regarding IL-33 (P value=.000).There was no statistically significant difference between chronic ITP patients and controls regarding IL-33 (P value=.769).There were no statistically significant positive correlation between IL-33 and [age (r=.057, P=.714), HB (r=.095, P=.540) and RBCs (.249, P=.103]. While There were statistically significant positive correlation between IL-33 and [WBCs (r=.398, P=.008), lymphocytes % (r=.377, P=.012) and Platelets (r=.537, P=.000).Conclusion: This study concluded that, IL-33 may contribute to the pathogenesis of ITP. It could be a potential biomarker that diagnose and provide a new therapeutic target for ITP therapy.