Dengue is probably the most important arthropod-borne viral disease in terms of human morbidity and mortality. We review the pathophysiology of thrombocytopenia and clinical bleeding in dengue across the spectrum of disease. The mechanisms of thrombocytopenia and coagulopathy are complex, involving platelet activation, procoagulant and anticoagulant arms of the coagulation system, complement, cytokines, and endothelial cells. Platelet counts do not correlate well with clinical bleeding. Although serious bleeding is rare, patients should be monitored closely for hemorrhagic manifestations and thrombocytopenia. Symptomatic thrombocytopenia may require platelet transfusion.