Embracing a lot of functions, metadiscourse markers are among the most significant factors which affect L2 writing quality. In the present study, whether explicit teaching of metadiscourse markers has any effect on EFL students' writing proficiency was investigated. The participants (N: 21) of the study included freshman students majoring in teaching English as a foreign language at a state university in Turkey. One group quasi experimental design was employed in the study. A process-genre based writing course syllabus, in which meta-discourse markers were taught explicitly was designed and implemented. Before the training, participants were asked to write an argumentative essay as pre-test. After the training, students were asked to write another argumentative essay about a different topic which was considered as post-test. In order to find out whether there was any difference between students former and later performances SPSS, a quantitative analysis method, was employed. Firstly, frequencies of metadiscourse markers used by the participants in their pre-test/post-test essays were calculated. Then, students' pre-test/post-test performances were compared. Findings of the study revealed that students made considerable progress in improving their writing as a skill especially in terms of achieving organization in their essays.