The current study aimed at developing prospective teachers' writing performance and self-efficacy through argumentation. Participants of the study were 30 EFL third year Faculty of Education students. They acted as one group. The researcher prepared a writing performance test, a self-efficacy scale and a manual. Having pre/administered the instruments of the study and taught using argumentation, the participants were post/administered the same instruments. Results showed that the use of argumentation significantly contributed to the development of students' writing performance and self-efficacy. The study presents some recommendations in the light of the results to highlight the effectiveness of argumentation in developing EFL prospective teachers' language learning. The study also suggests some topics for farther research