Protease inhibitors can prevent protein from degradation caused by protease activity. Blood plasma contains a variety of protease inhibitors. The objective of this study was to investigate the potential use of crude blood plasma from catfish (Pangasius hypopthalmus) and swamp eel (Monopterus albus) as protease inhibitors. The parameters observed were moisture content, protein content, ash content, inhibitory activity to trypsin and papain enzymes and protein profile of blood plasma. The inhibitory activity increased as the volume of blood plasma increased (25 µL, 50 µL, 75 µL, 100 µL). The inhibitory activity of blood plasma from catfish was 7.66-50.73% to trypsin enzyme and 20.34-83.05% to papain enzyme while the inhibitory activity of blood plasma from swamp eel was 9.49-46.35% to trypsin enzyme and 28.81-64.41% to papain enzyme. The highest inhibitory activity was demonstrated by swamp eel blood plasma with molecular weight between 19.84-174.14 kDa (13 proteins). Protein content of blood plasma from swamp eel (11.92%) was lower than catfish (16.63%) but resulted higher enzyme inhibitory activity. Further research can be conducted to carry out purification steps on blood plasma that are expected to show better inhibitory activity.