This study aimed at verifying the feasibility of transabdominal gastro-intestinal ultrasonography (TGIU) for predicting feeding intolerance (FI). This single-center prospective observational study comprising critically ill patients who were admitted to an intensive care unit (ICU) and received enteral nutrition through a nasogastric tube. TGIU parameters including gastric antral cross-sectional area (CSA) and acute gastrointestinal injury ultrasonography (AGIUS) score, were conducted on days 1, 3, 5, and 7 within the first week of starting enteral nutrition (EN). A total of 91 patients were eligible for inclusion and 57 showed FI. The incidence of FI was 28.6%, 41.8%, 29.7%, and 27.5% on days 1, 3, 5, and 7, respectively, and the incidence of FI was 62.6% within the first week of starting EN. Univariate logistic regression analysis showed that SOFA score, CSA, and AGIUS score, were significantly (P<0.05) associated with the FI on the same day. In the multivariate analysis including two variables, CSA, and AGIUS score were found to remain independent predictors for FI and 28-day mortality. An area under the curve (AUC) for TGIU predicted FI in the first week of starting EN (the cut-off of CSA ≥6.0cm2 yielded a sensitivity of 86.0% and specificity of 79.4%, and for AGIUS score ≥3.5 yielded a sensitivity of 87.7% and specificity of 82.4%). The predictive value of TGIU for 28-day mortality was higher than the SOFA score [0.827 (0.733-0.921) vs. 0.646 (0.519-0.774), P=0.001]. TGIU represented an effective means for predicting FI and 28-day mortality in critically ill patients. These results supported the hypothesis that persistent FI in critically ill patients is an essential determinant for poor prognosis.