Writing is one of the essential poles of language learning, and should be one of the senior interest, and concern to teachers, students, and researchers. The purpose of this study is to identify the effect of using the summarizing strategy on postgraduates 'learners. To develop the summary writing skills, two months implementation is applied to twenty Iraqi postgraduates 'learners, who are studying English as a foreign language (EFL) .The participants were from two departments in the college of political sciences at A-Nahrain University, Iraq, during the academic year 2018-2019. It was carried out in a single-group pre-post-test model only. A pre-test on summary writing conducted to participants a week before the summarizing strategy applied. The experimental process of the study lasted eight weeks, where the participants received 16 treatment sessions. Five different passages choose from their textbook (Headway for Academic Skills Level3), which was recommended by the university. The selected written passage for post-test was "globalization." The participants asked to summarize the passage within 45 minutes according to the new strategy. Data of the summary written test collected, and scored according to the five criteria such as; (grammar, vocabulary, organizing, content, and coherence). The findings of the study indicated that the summarizing strategy has a significant effect on postgraduates' learners in academic writing skills, so it is recommended that this strategy be applied in the curriculum of our schools and universities.