Background & Aims: Fecal calprotectin (FCal) is used as a noninvasive marker to rule out organic gastrointestinal diseases such as inflammatory bowel disease (IBD) from functional gastrointestinal disorders in children with chronic gastrointestinal symptoms. The aim of this study was to evaluate diagnostic accuracy of FCal for gastrointestinal inflammation and optimal cutoffs to differentiate IBD from eosinophilic gastrointestinal disorders (EoGD) and functional abdominal pain disorders (FAPD) in children with chronic gastrointestinal symptoms. Method: Between August 2015 and March 2017, a total of 253 children (123 boys and 130 girls, aged 2.9-17.8 years) were recruited and divided into the 3 study groups; FAPD (n=187), EoGD (n=28), and IBD (n=38). FCal, WBC, ANC, ESR, and hsCRP were measured at initial diagnosis in all subjects. Spearman correlation analysis was performed to evaluate the correlation between FCal and other inflammatory markers. Receiver-operating characteristics plot analysis was used to evaluate optimal cutoff levels of FCal. Results: Median FCal levels of FAPD, EoGD, and IBD in pediatric patients were 23.4 (11.5-1285.5) µg/g, 77.5 (11.5-2000) µg/g, and 2000.0 (60.4-2000) µg/g, respectively, which were significantly different among the 3 groups (p 0.001). FCal correlated positively with ESR (r = 0.569, p 0.001) and hsCRP (r = 0.480, p = 0.004) in the IBD group, and FCal correlated positively with ESR (r = 0.566, p = 0.004) in the EoGD group. A cutoff of FCal 90.3 µg/g distinguished EoGD from FAPD with a sensitivity of 54 % and a specificity of 83 %, and a cutoff of FCal 292.7 µg/g distinguished IBD from FAPD with a sensitivity of 92 % and a specificity of 95 %. A cutoff of FCal 677.4 µg/g distinguished EoGD from IBD in children with a sensitivity of 81 % and a specificity of 89 %. Conclusion: FCal is a useful and reliable noninvasive marker in differentiating EoGD from either functional abdominal pain or IBD in children manifesting with chronic gastrointestinal symptoms, when optimal cutoffs are applied.