This is an action research study that reports on using student portfolios in a second language (L2) Arabic class. The goal of this study was to examine the validity of using portfolios as an L2assessment procedure and to ascertain the effectiveness of portfolios as an L2 learning tool. In this class, portfolios replaced weekly quizzes, which counted for 30% of the final grade. Portfolios were also used to supplement the course textbook, namely Al-Kitaab (Brustad, Al-Batal, & Al-Tonsi, 1995).Data sources for the study included traditional tests grades, oral interview grades, portfolio grades, a sixteen-item survey, and students’ reflections at the end of the course. The findings indicate that there is a strong correlation between portfolio grades, on one hand, and written tests and oral interviews grades on the other hand. It was also found that students perceived using portfolios as an effective L2 learning tool.