Abstract <p>One of the goals of educational institutions is to make students problem-solvers. Hence, they design various tasks and initiate extracurricular activities to support learners’ thinking skills. Argumentation skill is one part of thinking and problem-solving skills, which support learners’ creativity, innovation, persuasion, and academic performance. Thus, the purpose of this research was to examine the effects of dialogic pedagogy on STEM students’ argumentation skills and motivation in learning English language courses. The participants were Bahir Dar University Science, Technology, Engineering, and Mathematics (STEM) students. The study was designed through a quasi-experimental design, in which two groups were selected and assigned to different groups. The data were gathered through oral presentation, key informant interviews, observation, and questionnaire, and the quantitative data were analyzed through independent t-test, One-Way Manova, and Paired sample t-test, and the qualitative data were analyzed through narration. The data indicated that dialogic pedagogy had a great impact on STEM students’ argumentation skills and motivation. The experimental group outperformed the comparison group in their oral argumentation skills and employed a higher level of claim formulation, provided reasons and evidence, supported their arguments, and had audience awareness. The data also confirmed that the experimental group improved their motivation skills, which the instruction supported the learners’ emotional engagement, interest and taking intellectual risks, active participation, and collaboration. Therefore, the researcher suggested that dialogic pedagogy could be an alternative instructional methodology to improve learners’ argumentation skills and motivation in learning English language skills.</p> Clinical Trial Number <p>Not applicable.</p>