This research was an attempt to investigate the influence of using portfolio assessment on students’ Learning English language in Qom Secondary Schools. The study participants were students of two intact English classes (N=68). The study used a pre-test post-test nonequivalent groups design with two groups. The methodological procedure adopted was to have the experimental group use the portfolio, with the control group using conventional assessment. The independent t-test computed between the means of the two groups signified that there was a statistically significant difference between the performances of the two groups on the achievement posttest. Moreover, a selfreporting questionnaire was employed after the treatment. The experimental results revealed that the use of the portfolio had significant positive influence on students’ language. However, the effect of peer-assessment performance was not significant.