The paper highlights the main aspects and characteristic features of teacher-teacher Wikis, which are considered to be the most effective teaching and learning tools. The research studies the effectiveness of using Wikis by teachers during collaborative lesson planning. It also traces the impact of teacher-teacher Wikis on the teachers' performance in the classrooms. Teaching collaboration has been studied as a crucial element as it involves planning and working together. Three EL teachers for the 5th elementary grade in elementary schools in Riyadh were chosen to be the study participants. The research was carried out during a four-week period. In order to collect data and achieve the study's goal, four tools were used: a questionnaire, observation, interview, and text analysis. The research results proved the idea that using teacher-teacher Wikis in collaborative lesson planning is effective and improves teachers' performance.