This study aimed to find out the effects of collaborative writing strategies on ESL learners' writing fluency which specifically focused on content elaboration and organization in the essays. This qualitative study employed an action research design and the participants were twenty form four pupils (age 16) from one of the secondary schools in Kluang, Johor. The participants underwent sequential and parallel collaborative writing strategies throughout 12 lessons which revolved around 6 weeks after their first writing task. They sat for their final writing tasks after 6-week of the implementation of collaborative writing strategies. After 6 weeks of 12 lessons the participants sat for their final writing task which had the same question. The analysis of the first and final writing task was used to find out the effects of collaborative writing strategies on the elaboration of contents and organization of their writing. The finding revealed that learners showed moderate or significant changes on the elaboration of contents and organization in their final writing. Therefore, collaborative writing strategies could be one of the timeless and feasible strategies that teachers can put into practice in enhancing 21 st century learners' writing fluency.