Learning writing in ESL and EFL classes is usually associated with teaching grammar, writing paragraphs, essays, etc. Although acquiring these skills help students develop their formal writing abilities, these activities are assumed dull and meaningless for many of them. Introducing more modern, meaningful, communicative activities to EFL contexts such as Iranian schools may yield multi –purpose results, among those, motivating students particularly the reluctant ones to write without having the fear to be judged or punished and developing students’ positive attitudes toward writing, can be mentioned as the most important aims. The objective of this study was to investigate the effect of Dialogue Journals Writing (DJW) as an informal, communicative activity on writing proficiency of intermediate Iranian high school students and their attitudes toward writing .The participants were 42 Iranian female students. The students in the experimental group wrote dialogue journals daily in a period of two months while the students in the control group wrote weekly compositions. An attitudinal questionnaire was administered twice, before and at the end of the project and both groups took pre- and post-tests. The results revealed that DJW improved students' writing although the amount of improvement was not very significant and they hold positive attitudes toward DJW as students believed that journals enhanced their motivation to write and increased their fluency.