Abstract T his research aimed to develop the skills of argumentative written expression in French using a weblog of a sample of students of the fourth year, French department, at the Faculty of Education in Dakahlia, Al-Azhar University. The research sample consisted of (60) students, who were randomly divided into two experimental and control groups, each group contain thirty students. After the application procedures, the search resulted in a set of results, the most important of which are: The effectiveness of weblogs in developing argumentative written expression in French among the students of the fourth year, French department at the Faculty of Education in Dakahlia, Al-Azhar University, where a statistically significant difference was found at the level (0.01) between the mean scores of the experimental group students in the pre/post test of argumentative written expression, for the benefit of the post test, as well as the presence of a statistically significant difference at the level (0.01) between the mean scores of the experimental group students and the group control students in the post-test of the argumentative written expression test for the benefit of the experimental group. This confirms the effectiveness of weblogs developing argumentative written expression in French of the research sample.