Background & Objectives: Capillary leak syndrome (CLS) is a critical complication of dengue fever. Early recognition is essential for timely intervention.. Purpose of the study is to analyze the roles played by portal venous ultrasonography and color Doppler indices in detecting and predicting capillary leak syndrome in patients with dengue fever and correlating these imaging findings with clinical outcome. Materials and Methods: It is a prospective observational study conducted on 60 dengue fever cases that were serologically confirmed. The study was conducted from September 2022 to December 2023.On admission Grey –scale abdominal ultrasonography and portal venous Doppler was performed. Portal vein (PV) diameter, cross-sectional area (CSA), peak venous velocity, and congestion index (CI) were assessed and plasma leakage features were recorded sonographically. Results: Capillary leak syndrome developed in 54 (90%) patients. Gallbladder wall oedema detected in 56.7% cases and was the most frequent ultrasonographic sign. It followed by pleural effusion (48.3%) and ascites (35%). CLS patients exhibited significantly lower portal vein velocity (mean 17.41 ± 4.02 cm/s) compared to those without CLS (26.66 ± 3.33 cm/s) (p < 0.001). Congestion index was significantly elevated in CLS (0.103 ± 0.034). ROC analysis showed highest predictive accuracy for CI (AUC 0.898), followed by velocity (AUC 0.866). Conventional ultrasonographic features demonstrated high specificity but lower sensitivity. Conclusion: Portal venous Doppler parameters, especially velocity and congestion index, provide strong early indicators of CLS and outperform traditional ultrasonographic features in diagnostic accuracy. Clinical Impact: Portal venous Doppler integration in case evaluation can be added to early risk stratification in dengue fever and can potentially reduce morbidity and progression to shock.