This article presents the state of the art on the use of portfolios as instruments to evaluate plurilingual students in foreign language classrooms. It presents the concept of the European Language Portfolio and discusses how it encourages plurilingual learning and assessment. Based on a literature review, the authors argue that the European Language Portfolio is a pedagogical tool for enhancing learners' plurilingual and metacognitive competences and encouraging their autonomy. At the same time, it allows internal classroom differentiation. Following the analyses of empirical studies using the European Language Portfolio, the authors conclude that its main strengths lie in the use of concrete “can do” descriptors for evaluation and its ability to foster students' reflection on their plurilingual identity and language learning strategies, including cross-linguistic strategies. Using the European Language Portfolio, teachers can evaluate plurilingual students' cross-linguistic competences through the development of specific descriptors and their personal reflections.