Background: According to insufficient clinical studies concerning association between Gastro Intestinal Failure Score (GIF Score) and mortality rate of ICU admitted patients, the aim of this study was to determine predicting value of GIF Score in mortality rate of ICU admitted patients. Materials and methods: In this cross-sectional study, 357 patients who were ≥18y/o and were admitted in ICU during 72 hrs were enrolled in the study. For all patients, informed consent form, demographic data sheet and physical examination were completed and intra-abdominal pressure, GIF Score of first week and mortality rate of first week and 28th day were recorded. All collected data was analyzed by SPSS 16 software. Results: In this study mortality rate of 7th and 28th day were 11.5% and 29.7%, respectively. Incidence of high intra-abdominal pressure (IAH) and abdominal compartment syndrome (ACS) were 34.7% and 6.2%. The mean GIF Score during first week was 1.346(SD 0.935). All of these variables were significantly correlated with mortality of 7th and 28th day. Also in logistic regression model, IAH, ACS, GIF score were predicting variables for mortality of 7th and 28th day in ICU admitted patients. Conclusion: According to the results GIF score was significantly correlated with mortality rate of 7th and 28th day in ICU admitted patients. It seems further multi central studies are essential