Background: Fibroblast growth factor 19 is a protein which is encoded on FGF19 gene and acts as a hormone, which regulates bile acid synthesis, with effects on glucose and lipid metabolism. This study aimed to measure serum level of FGF19 to investigate its potential role as a diagnostic biomarker for gastrointestinal -liver dysfunction in neonatal sepsis. Methods: This case-control study was conducted on 100 full term neonates from the Neonatal Intensive Care Unit at Benha University Hospitals. They were divided into 2 equal groups: Sepsis group: included 50 full term neonates diagnosed as sepsis (clinically and laboratory). Control group: included 50 full term neonates matched sepsis group in age and sex. All newborns were subjected to full history taking, complete clinical examination, laboratory investigations and specific laboratory investigations (FGF19 using ELISA). Results: FGF19 level was significantly lower in sepsis group compared to control group (231.36 ± 66.7 vs. 349.49 ± 87.81 Pg/ml, P value