Argumentation skills are important for students to analyze and evaluate critical information, especially in complex science issues. Socio-Scientific Real-world Inquiry [SSRI] learning helps students develop deep scientific understanding and the ability to build evidence-based arguments in a real context. This study aimed to examine the effectiveness of SSRI learning model in improving argumentation skills. The research design used was quasi-experimental with a pretest-posttest non-equivalent control group design, in which argumentation skills were measured before and after the intervention in two groups: an experimental group consisting of 44 students who received learning with the SSRI model and a control group comprised of 46 students who followed the inquiry learning. Analysis of changes in pretest and posttest scores on each aspect of argumentation skills was conducted using a paired sample t-test. In contrast, comparison of posttest scores between the two groups was analyzed by independent sample t-test. Analysis of the effect size on each aspect of argumentation skills in the control group and experimental group using Cohen's Effect Size method. The analysis results showed that the SSRI learning model was more effective in improving argumentation skills than the inquiry learning. These results indicate that SSRI can be an effective learning approach for educators and educational policymakers in an effort to develop argumentation skills that are crucial for individuals.