This research study investigated students' perceptions toward the use of portfolios as well as documenting the progress of a portfolio assessment in a classroom-based setting of Thai EFL undergraduate students. The 25 first-year students who had enrolled in an English foundation course offered at a public university were the participants. These participants completed two types of essays, which comprised eight drafts in total for compiling the portfolios. Reflective journals, a perception questionnaire, a semi-structured interview, and a portfolio self-assessment form were utilized to collect data so that the perceptions toward the use of portfolios could be examined. The quantitative data from the perception questionnaire were analyzed by descriptive statistics (mean scores and standard deviation). The qualitative data from the reflective journals, semi-structured interview, and portfolio self-assessment form were analyzed by means of content analysis. Moreover, the progress of the eight drafts of two types of essays was analyzed by repeated measure ANOVA. It was found that the participants had positive perceptions toward the use of portfolio assessment, and they wrote significantly better essays. In sum, portfolio assessment can be an effective alternative choice in a classroom-based setting.