Histone H1 and its C-terminal lysine rich fragments were recently found to be potent inhibitors of furin, a mammalian proprotein convertase. However, its role in the regulation of furin-dependent proprotein processing remains unclear. Here we report that histone H1 efficiently blocks furin-dependent pro-von Willebrand factor (pro-vWF) processing in a dose-dependent manner. Coimmunoprecipitation and immunofluorescence studies confirmed that histone H1 could interact with furin, and the interaction mainly took place on the cell surface. We noted that histone H1 was released from cells undergoing necrosis and apoptosis induced by H2O2. Our findings suggested that histone H1 might be involved in extracellular and/or intracellular furin regulation.