Advancements in science, technology and education highlight the importance of engaging science students in Socio-Scientific Issues (SSI)-based argumentation and enabling them to make informed decisions. The purpose of this research was to explore the efficacy of SSI- based argumentation in the context of biology (genetics) for improving grade-IX students’ argumentation skills focusing on complexity and quality of argumentation. The study was conducted as a pre-experiment in one school. To meet the needs of the study, all of the grade-IX students (n = 44) of biology group were recruited as sample. However, 38 students provided their responses on writing frames for both the pre- and post-test. After being taught a unit of 12 (45-minutes each ) lessons on genetics, students were explicitely instructed argumentation skills in one 45-minutes each session and engaged in oral and written argumentation in further three 45-minutes lessons. Data were gathered through pre- and post-instruction with detailed written students’argumentation on writing frame which were consisted of SSI-based scenario with guiding questions . In order to answer the two research questions, the data were analyzed twice using separate frameworks for complexity and quality of argumentation. The findings indicated an increase in the argumentation skills of grade-IX students. The difference between pre-test to post-test complexity of argumentation was considered significant (Wilcoxon signed ranked W = 553; Z = -4.940; p < 0.01). Also, the effect size (r = 0.80) was considered as large. Similarly, the difference in the level of quality of grade-IX students’argumentation was also found significant (Wilcox on signed ranked W = 528; Z = -5.005; p < 0.01) with large (r = 0.83) effect size. The results are important as strategy of teaching of science through argumentation about SSI has been found efficacious for improving complexity and quality of students’ argumentation skills in the context where most of the students are unaware of SSI-based argumentation. The finding are also important because they add to the literature for the area where there has been found dearth of research in the field of SSI based argumentation.