As there are limited studies examining relationships between argumentation-based teaching approach and critical thinking and argumentation skills in social studies, the aim of this study was to examine the effects of argumentation-based teaching approach on students' critical thinking disposition and argumentation skills, and the relationship between students' argumentation skills and critical thinking disposition. We used a quasi-experimental design with pretest-posttest equivalent control groups. The participants of this study were 94 seventh grade students from three different classrooms in a middle school in Erzurum district of Turkey. We utilized University of Florida Engagement, Maturity and Innovativeness Critical Thinking Disposition Instrument (UF/EMICTDI) to identify students' critical thinking disposition and argumentation activities to document students' argumentation skills. We used one-way ANOVA and multiple comparisons Tukey tests to analyze the data obtained via the UF/EMICTDI, correlation and regression analysis to investigate the relationships between students' argumentation skills and critical thinking disposition. Argumentation Evaluation Rubric was used in order to evaluate the arguments that the students formed. Results showed that there was no statistically significant difference between students' pretest critical thinking disposition scores in the experimental and control groups but there was a statistically significant difference between students' post-test critical thinking disposition scores. Additionally, we observed that students' argumentation skills enhanced throughout the study, there was a statistically significant positive relationship between students' argumentation skills and critical thinking disposition, and argumentation skills variable was the predictor of critical thinking disposition. We recommend future research studies to examine the effects of the argumentation-based science learning approach on different higher-order thinking skills. Additionally, in social studies classes, similar activities employed in this study on "Population in Our Country" unit can be used in teaching different topics/units in order to improve students' argumentation skills.