the present study was conducted to investigate the effect of using model essays on the development of writing proficiency of iranian pre-intermediate efl learners. to fulfill the purpose of the study, 55 pre- intermediate learners of parsa language institute were chosen by means of administering proficiency test. based on the results of the pretest, two matched groups, one as the experimental group and the other as the control group were formed. these learners, were pre tested through a writing task. each participant was asked to write about a topic. then, participants in the experimental group studied a model essay about the writing task and they underlined or took notes about those aspects of language that they noticed in the model essay written about the same topic. it means that, model essays were accompanied by the teachers explanations. after seven sessions of treatment, the two groups were post tested through a writing task, the same as pretest. the scores of the participants demonstrated that the experimental group outperformed the control group. after running a t-test for comparing the mean score of two groups, it was concluded that using model essays has a significant effect on the development of writing proficiency.