Background: Argumentation is accepted by many science educators as a major component of science education. Many studies have investigated students' conceptual understanding and their engagement in argumentative activities. However, studies conducted in the subject of chemistry are very rare. Purpose: The present study aimed to investigate the effects of argumentation-based chemistry lessons on pre-service science teachers' understanding of reaction rate concepts, their quality of argumentation, and their consideration of specific reaction rate concepts in constructing an argument. Moreover, students' perceptions of argumentation lessons were explored. Sample: There were 116 participants (21 male and 95 female), who were pre-service first-grade science teachers from a public university. The participants were recruited from the two intact classes of a General Chemistry II course, both of which were taught by the same instructor. Design and methods: In the present study, non-equivalent control group design was used as a part of quasi-experimental design. The experimental group was taught using explicit argumentation activities, and the control group was instructed using traditional instruction. The data were collected using a reaction rate concept test, a pre-service teachers' survey, and the participants' perceptions of the argumentation lessons questionnaire. For the data analysis, the Wilcoxon Signed Rank Test, the Mann-Whitney U-test and qualitative techniques were used. Results: The results of the study indicated that an argumentation-based intervention caused significantly better acquisition of scientific reaction rate-related concepts and positively impacted the structure and complexity of pre-service teachers' argumentation. Moreover, the majority of the participants reported positive feelings toward argumentation activities. Conclusions: As students are encouraged to state and support their view in the chemistry classroom when studying reaction rate, it was observed that their understanding increased in terms of both the context and the quality of the argumentation that they produced. In light of the findings, it is suggested that argumentation activities should be developed to promote students' science content knowledge and argumentation skills.