This study investigated how the scientific competencies advocated by the Programme for International Student Assessment (PISA) could be improved by using online argumentation. An online argumentation system served as an aid for argumentation instruction and activities among students during the experiment. Seventy-one 10th grade high school students took part in this study. A quasi-experimental design was adopted and qualitative and quantitative analyses were used. The results showed that using the online argumentation system to conduct argumentation instruction and activities could improve the students' PISA scientific competencies. The experimental group students outperformed their counterparts in terms of mean scientific competencies. Finally, this study proposed suggestions related to argumentation research and science instruction. [For the full proceedings, see ED562127.]