Persuasive writing is one of the main writing genres secondary students are required to master. However, while the students can naturally argue verbally and in an informal setting, they lack the skill to compose a persuasive argument for academic purposes. The main problem is that students can barely construct an argument while composing a persuasive essay. The objectives of this study are to verify the effectiveness of the secondary students' arguments according to Toulmin's Model. A sample size of 150 students from three different secondary schools in the Klang area was chosen for this study. The students were instructed to write an essay according to a set of essay prompts provided by the researcher. The Toulmin's Model was employed as the main tool to analyze the essays to tag and label the persuasive elements that were used by the students while writing the essays. The findings reveal that the students are mostly able to apply the basic persuasive elements (grounds, claims and warrant) but do not take full advantage of the optional elements (qualifier, rebuttal and backing). It is concluded that new strategies and a new model need to be proposed to help train the students to improve their persuasive writing skills.