This study presents a case study of academic discourse socialization in a Japanese EFL student in a research seminar course to understand the content of a scholarly book in English. Drawn on theoretical perspectives of language socialization and community of practice, an 8-month case study investigated how the participant was socialized into the disciplinary community through her study of an English-language scholarly textbook in a research seminar course. Data were collected from weekly reflection journals, a final narrative assignment, and individual interviews with the participant. These data were coded to identify the thematic categories. Findings showed that the participant came to be socialized into her specialized community through interacting with peers in the classroom and cultivating her expertise. Then, the participant created a social network outside the classroom, encouraging casual discussions with her friends on topics she was learning about in class. Based on the findings, this article suggests that there are parallels between academic discourse socialization in EFL contexts and those in English-speaking contexts, beginning to bridge a gap in research across learning settings. Implications for pedagogy and future research are discussed.