The aim of this study is to investigate the effectiveness of portfolio assessment on EFL learners' reading comprehension ability. 50 EFL language learners at intermediate level all female from a private institute were selected for this purpose. Then they were randomly divided into the control and experimental group. The control group received the traditional assessment while the experimental group received the portfolio assessment. Two reading comprehension tests as pretest and posttest were given to the students of both groups to find out their reading comprehension ability at the beginning and at the end of the study and the treatment. The results of data analysis revealed that the students in the portfolio assessment group outperformed the students in the control group in their reading comprehension ability. Finally the findings of this study suggest that portfolio assessment empowers students' reading comprehension ability.