Backgrounds: Budd-Chiari Syndrome (BCS) is a hepatic venous outflow obstruction at any level between the hepatic veins and the right atrium Objective: to assess quantitative D-dimer levels in BCS cases and using it as a biomarker in diagnosis of thrombotic events. Methodology; Group I included (18) patients with primary BCS. Group II; included (22) patients with primary BCS with newly reported thrombotic event, as well as Control group. For all cases; complete lab, viral markers, thrombophilia work up, D-dimer level assessment as well as radiological evaluation were done. Results: Assessment of D-dimer serum levels shows a high statistical difference between the 3 studied groups (P<0.01). D-Dimer equals or more than to 1.65 can predict new thrombosis events with a sensitivity and specificity values (93.8% and 87.5%) respectively. Conclusion: D-dimer level was significantly higher in BCS patients on medical treatment who developed new thrombosis than patients without event of new thrombosis.