The aim of this study was to calculate the corrected rate of reflux in children with gastroesophageal reflux (GER)-like complaints by 24-hour pH monitoring and esophagogastroduodenoscopy (EGD), and to determine the utility of mean platelet volume (MPV) and red cell distribution width (RDW) as diagnostic biomarkers of GER disease (GERD) in children. The subjects in this prospective study were 109 children, 6 to 18 years old. Of them, 74 subjects were with GER symptoms and 35 healthy controls. The subjects were divided into three groups: those who underwent 24-hour pH monitoring (Group 1), those who underwent EGD together with pH monitoring (Group 2), and the healthy controls (Group 3). The results of pH monitoring and EGD and hematological parameters with controls were compared between Groups 1 and 2. In Groups 1 and 2, the overall rate of reflux was 40%, of esophagitis was 27.8%, and of Helicobacter pylori infection was 31.2%. The MPV and RDW cut-offs in subjects with reflux were <= 8.97 (sensitivity 89%, specificity 89%) and <= 12.78 (sensitivity 80%, specificity 97%), with an area under the Receiver Operating Characteristic (ROC) curve +/- standard error (AUC +/- SE) = 0.917 +/- 0.027 (P < 0.001) and AUC +/- SE = 0.866 +/- 0.036 (P < 0.001), respectively. The endoscopic procedures are not practical due to being invasive and expensive. However, hemogram is a simple test which can be performed in an outpatient clinic. MPV and RDW calculated in hemogram could be easy, cost-effective, and high sensitive new biomarkers that can be used in children with GERD.