Propolis is thought to help prevent thrombotic and related cardiovascular diseases in humans, but this has not yet been definitively demonstrated. Elevated levels of plasma plasminogen activator inhibitor 1 (PAI-1), an inhibitor of fibrinolysis, predisposes individuals to a risk of developing thrombotic diseases. Plasma PAI-1 increases under inflammatory conditions such as infection, obesity and atherosclerosis. Maintaining physiological PAI-1 levels in plasma might represent a promising intervention for treating various diseases. The present study examines the effects of propolis and its components including flavonoids and derivatives of benzoic, cinnamic and quinic acids, on the increase in PAI-1 induced by inflammation. Propolis inhibited the increase in PAI-1 induced by tumour necrosis factor (TNF)-α in HUVEC culture medium. We also showed that the flavonoid chrysin is an active constituent. Both propolis and chrysin inhibited the increase in PAI-1 induced by LPS in mouse plasma. Thus propolis and its constituent, chrysin, inhibited PAI-1 production. The present findings confirmed the potential of propolis and its constituents in treating or preventing thrombotic disorders, or as an antithrombotic food supplement.