Present study aimed to explore the impact of formative portfolio assessment on Saudi EFL learners' overall writing performance. The study reviewed literature of prevailing assessment challenges including the formative role of portfolio assessments to develop an understanding of the nature of assessments and various issues related to assessment practices. The current research applied formative portfolio assessment (FPA) technique as an intervention material in the ongoing preparatory Intensive English Language course and utilized semi-structured interviews to elicit qualitative data from students. The findings of the study suggest: formative portfolio assessment inspires autonomous learning among students by empowering them taking more control of the learning and assessment process.