Diary writing is a very effective tool for both students and teachers since this technique enables students to think on what they have learned, how they have learned it, what kind of difficulties they have when they need to write in English or what helps them to overcome these difficulties in the process of learning English. Furthermore, teachers can learn from students’ diaries about their limitations and faults in writing and help them to remove them. They can also find out what teaching strategies students prefer the best and use them in their teaching. The purpose of this article is to discuss about diary writing used in the Course of Academic Writing for TEFL learners and analyse the effect of this approach on developing writing skill. The results revealed that diary writing as a tool for self-reflection can improve writing skill better than mere teacher written error correction.