Abstract This study aimed to identify the effectiveness of collaborative writing wiki in developing EFL writing skills and reducing apprehension of al Azhar secondary stage students. The study used certain instruments: an EFL writing skills questionnaire, an EFL writing pre-post-test, an EFL writing skills rubric, and an EFL writing apprehension inventory. The study came up with a number of results. The participants consisted of 60 first year Al-Azhar secondary stage students. They were divided into two groups; the control group which was instructed via traditional teaching method and the experimental group which was instructed via collaborative writing wiki. There was a statistically significant difference between the mean scores of the control group and the experimental group on the post applications of the EFL writing skill test in favor of the experimental group. There was a statistically significant difference between the mean scores of the experimental group pre and post applications of the EFL writing skill test in favor of the post application. There was a statistically significant difference between the mean scores of the experimental group and the control group on the post applications of the writing apprehension inventory in favor of the experimental group. There was a statistically significant difference between the mean scores of the experimental group pre and post applications of EFL writing apprehension test in favor of the post application. The study provided evidence for the effectiveness of using collaborative writing wiki in developing wringing skills and reducing writing apprehension. Key words: wiki, collaborative writing, EFL writing skills, apprehension