The purpose of this research was to examine the impact of employing concept mapping at a pre-writing stage on English as a foreign language (EFL) students' ability to generate better argumentative essays. Thirty-eight participants were randomly assigned to two groups participating in Writing II course at Al-Quds Open University (QOU). Both groups had the same teacher. The control group received instruction as required in the textbook only, and the experimental group were additionally required to construct concept maps at the pre-writing stage and compose essays based on the constructed maps. All participants were required to sit for pre- and post-tests to track their writing performance before and after the experimental group took a tutorial on how to create concept maps. After the implementation of the intervention, comparison of the students' mean scores of the pre- and post-tests showed a statistically significant improvement in the experimental students' ability to generate better argumentative essays in terms of point of view, unity and coherence, development, organization, and thinking. The results highlight the effectiveness of employing concept mapping as a focused instructional strategy at the pre-writing stage in developing EFL students' writing skill. Pedagogical implications for using concept mapping in EFL writing classes are considered.