The purpose of this study was to examine the extent to which instruction in the Toulmin model of argument (TMA) helps students develop their argumentation skills in their speaking classes using debate activities. The study employed a pretest-posttests control group design in which participants were assigned to the experimental (EG) and control groups (CG). The participants were 80 students of the Department of English Language and Literature, Faculty of Arts, Menoufia University. The study included an intervention which was the implementation of the TMA in EFL speaking classes. Both groups were given a pretest before the experiment in which they were required to present arguments while debating and then a posttest after the ten weeks of treatment administration. A rubric was used by two raters and the researcher to score the speech arguments of the participants in the pre-and posttests on the target features. The results of the data analysis revealed that, in comparison to the pretest, the argumentative speeches from the posttest featured more rich and sophisticated reasoning. In terms of argumentation skills, the experimental group outperformed the control group significantly. This demonstrates that teaching the Toulmin model enhanced learners' comprehension of argumentation elements, their function, and application.