Infection with dengue virus (DV) can result in dengue hemorrhagic fever and dengue shock syndrome, where patients suffer from bleeding and plasma leakage involving endothelial cells. Angiopoietins (Ang) 1 and 2 are important angiogenic factors that affect endothelial barrier integrity. In this study, DV was observed to induce endothelial leakage at multiplicity of infection of 10 in primary human umbilical vein endothelial cells (HUVEC) with interendothelial gap formation. Immunostaining of vascular endothelial cadherin (VE-cadherin) and zona occludin 1 (ZO-1) showed the absence of these endothelial junctional proteins at the cell-cell contact zones between adjacent cells. In addition, Ang1 that is required for protecting against endothelial hyperpermeability was found to be down-regulated during DV infection. Treatment with increasing concentrations of recombinant Ang1 was shown to prevent DV-induced endothelial hyperpermeability in a dose-dependent manner by preventing the down-regulation of VE-cadherin and ZO-1 at cell membrane. In contrast, the expression of Ang2, the natural antagonist of Ang1, was observed to be up-regulated during DV infection. Recombinant Ang2 added to HUVEC at non-toxic concentrations showed decreased in transendothelial electrical resistance reading and the down-regulation of VE-cadherin and ZO-1. These findings suggest that DV reduces the expression of Ang1 and enhances the expression of Ang2 in endothelial cells and that this imbalance of Ang 1 and Ang 2 may play a contributing role to the increased permeability of human primary endothelial cells during DV infection.