This classroom-based research is intended to examine the effectiveness of employment of the Toulmin model in teaching argumentative writing in a Turkish EFL university classroom. Argumentative writing samples by 16 freshmen were collected before and after the instruction. During the instruction, a variety of one-hour activities incorporating the Toulmin model were integrated into the regular 10-week teaching curriculum, including explicit instruction of the Toulmin model, awareness-raising about the Toulmin model and its elements with carefully selected reading passages, class debate on controversial issues, and identification of Toulmin elements in published argumentative essays. The results showed that students’ argumentative papers improved after instruction, presenting more enriching and complex argument structures, exhibiting the important elements in argumentation, such as opposing views and rebuttals, which were almost non-existent in their previous argumentative papers. The students also felt that the instruction had empowered them to write argumentative papers in the future.