Dengue virus (DENV) causes fever and severe haemorrhagic symptoms in humans. The DEN2 16681 strain, derived from a dengue haemorrhagic fever patient, has been widely used in studies related to DENV pathogenesis, such as mouse and non-human primate haemorrhagic models and human vascular endothelial-cell permeability. To clarify the entry mechanism of the 16681 strain, we characterized a novel cell receptor for this strain. Our two major findings were as follows: firstly, the SDC2 membrane protein was an effective DEN2 16681 receptor in a cloned K562 cell line. Secondly, a heparan sulfate (HS) glycochain (of four glycochains in SDC2) is the specific binding site of DENV and seems to be involved in tissue-culture adaptation. Our findings present an entry mechanism that could be implicated for DENV adaptation and HS-mediated DENV infection.