Dengue viruses are classified into four serotypes. Here, we report a 1.7 Å crystal structure of a recombinant dengue-3 envelope protein domain III (ED3), which contains most of the putative epitopes. Although the fold was well conserved, we found that a local backbone deformation in the first β-strand, which contains the putative epitope-1, occurred upon domain isolation. Furthermore, a comparison with dengue-2 ED3 indicated a large structural change by as much as 4.0 Å at Asp(662), located in epitope-2. These minute structural and surface properties changes observed in the high resolution ED3 structure represent potential determinants for serospecificity and epitope recognition by antibodies.