Background: The decrease in the level of gelsolin was related to the prognosis and severity of many diseases, such as hyperoxic lung injury, sepsis, bronchopulmonary dysplasia (BPD), and intracranial hemorrhage. Aim of the work: The aim of the current study was to study the role of plasma gelsolin level in diagnosis of pneumonia in infant and children. Methods: A Prospective Case control study was conducted on 50 subjects whom admitted to the Zagazig University Children Hospital and Microbiology and Immunology Department, Faculty of Medicine in collaboration with Molecular Biology Unit Zagazig Scientific and Medical Research Center during the period from September 2018 to April 2019, the study included 50 participants were divided into 2 groups; Group (I): 40 patients with Pneumonia, and they were classified into 3 subcategories groups (mild - moderate - severe) according to PRESS scorning system and Group (II): 10 apparently healthy subjects as a control group. Result: There was a high statistically significant difference between patients and control group as regard hemoglobin level, TLC, CRP and lymphocyte count, there was a statistically significant difference in gelsolin level between patients group and control group. Conclusion: gelsolin serum level decrease in pneumonia and can be used as diagnostic and prognostic marker with good statistical performance.