Portfolios have been utilized in the teaching and learning of English of speakers of other languages as a tool for process-based writing and as an alternative form of summative assessment. While extensive research has been focused on the implementation of portfolios in English as a foreign language (EFL) writing, there has been limited attention to their use for graduate students in a Korean EFL EMI (English-medium instruction) context. This study aims to address this gap by examining portfolios as a means to enhance EFL writers' awareness at the graduate school level and to facilitate autonomous learning. A case study is conducted on a single EMI course focused on academic English writing for graduate students majoring in applied linguistics. A portfolio assessment framework is utilized to delineate and reflect on the case study. The pedagogical choices regarding procedures and the selection of portfolio topics are discussed. Lastly, practical classroom considerations for implementing portfolios are suggested, along with implications for EMI writing courses at the graduate school level.