This classroom-based research is intended to introduce the Toulmin model in the teaching of argumentative writing in a Turkish EFL university classroom and to examine its effectiveness. Sixteen freshmen’s argumentative writing samples 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 argumentative papers. The results showed that students’ argumentative papers improved after instruction, presenting more enriching and complex structures, exhibiting the important elements in argumentation, such as opposing views and rebuttals, which were almost non-existent in argumentative papers before the instruction. The students also felt that the instruction had empowered them to write argumentative papers in the future.