abstract the current study set out to address the issue as to whether the implementation of portfolio assessment would give rise to iranian pre-intermediate efl learner autonomy. participants comprised 60 female in pre-intermediate level within the age range of 16-28.they were selected from among 90 language learners based on their scores on language proficiency test -key english test. then, they were randomly divided into two groups each consisting 30 participants. an independent sample t-test confirmed their homogeneity. moreover, they were homogenized in terms of autonomy through employing a researcher-made questionnaire. another independent sample t-test was run to ascertain their homogeneity in that respect. the portfolio assessment was integrated into the experimental group while traditional assessment was assigned to the control group. both quantitative and qualitative procedures were used for data collection and analysis. data were collected by means of a researcher-made questionnaire, a semi-structured interview, and participants’ portfolios. quantitative data were analyzed using spss version 15 and the statistical techniques of t-test. qualitative data were analyzed inductively through content analysis. the recurring themes emerging from the interview and participants’ portfolios were compared with the findings of the questionnaire. the results of both quantitative and qualitative data analysis revealed that portfolio assessment enhanced learner autonomy in experimental group significantly, and offered them an opportunity to reflect upon their learning process, growth, and progress overtime. drawing on the findings, some pedagogical implications were proposed and finally, some avenues for future researches were highlighted.