Background. Although the exact pathophysiology of functional gastrointestinal diseases remains unclear,numerous etiologies have been blamed, including visceral hypersensitivity, gastrointestinal motility disorders,psychological factors, intestinal mucosal inflammation, intestinal microbiota, and post-infectious syndromes.In the present study, we aimed to evaluate pancreatic insufficient patients diagnosed with functional abdominalpain-not otherwise specified (FAP-NOS) according to Rome IV criteria. Methods. The study included a total of 110 patients aged 4-17 years who were diagnosed with FAP-NOSaccording to Rome IV criteria. The control group consisted of 80 patients with no gastrointestinal disorders andchronic diseases. Glucose, amylase, lipase, pancreatic amylase, immunoreactive trypsinogen (IRT) and fecalelastase (FE-1) levels were examined for each patient.Results. No significant difference was found between the two groups with regard to lipase, pancreatic amylase,IRT, and serum glucose levels. However, the amylase levels were significantly higher and the FE-1 levels weresignificantly lower in the study group compared to the control group (p=0.007 and p<0.001). The cut-off valuedetected in in ROC analysis for the diagnostic value of FE-1 in predicting FAP-NOS was found to be 140.107μg/g. Based on this value, the sensitivity, specificity, PPV, and NPV of FE-1 were 82.1%, 66.2%, 77%, 73%,respectively. Accordingly, the likelihood of FE-1 in providing a positive value in patients with FAP-NOS wasalmost 9 times higher than in individuals without FAP-NOS.Conclusions. FE-1 levels were significantly lower in children diagnosed with FAP-NOS and we consider thatthis difference could be attributed to malabsorption secondary to dysbiosis as there is not enough data.