Abstract: In order to purify protease(s) produced by Emericella nidulans AUMC 9198, several steps were performed including ammonium sulphate precipitation at 80% and chromatography on Sephadex G-100 and on DEAE-cellulose columns. The optimum pH, temperature, pH and thermal stability were pH 8, 55°C, pH 7-10 and up to 55°C respectively. Protease activity was completely inhibited with PMSF and Hg2+ while not affected with EDTA. The purified enzyme had a Vmax value of 595 U/ml and Km value of 1.092 mg/ml. Anticoagulant potency of the purified serine protease recorded prolonging action on the extrinsic coagulation pathways using prothrombin time (PT) bioassay. Key words: Emericella nidulans, proteases, purification, anticoagulant potency.