The present study intended to examine the potential role of process-based approach on improving the writing skill, critical thinking ability, and autonomy among Iranian EFL learners. To this end, 60 Iranian intermediate EFL students aged 18-23 were selected from among 120 available Iranian EFL learners. The students were selected based on the result of the Oxford Placement Test (OPT) and further were divided into two groups of control and experimental. Initially, a questionnaire of autonomy was employed by the researchers to retrieve the participants’ opinions in the experimental group about the extent to which they considered themselves autonomous. Next, a pre-test for assessing critical thinking ability and a pre-test for assessing writing skill of the participants were administered to both groups. The control group only received the conventional classroom instruction on writing skill which was based on product-based approach, but students in the experimental group students were taught to write using the process-based approach. After 12 weeks of instruction based on process-based approach, the questionnaire of autonomy was again administered to the experimental group; and a post-test for critical thinking and a post-test for writing were administered to the participants in both experimental and control group. The data collected were subject to statistical analysis. The results revealed that process-based approach was of positive effect on learners' writing proficiency, critical thinking ability, and autonomy.