Second language (L2) classrooms are venues for learners to construct their identities, which are socially, culturally, politically and historically situated. Informed by the theory of community of practice (COP), this paper examines how two Saudi first-year students who are pursuing their master degree in TESOL at American Universities shape and negotiate their identities (i.e., participation and membership) in their new academic communities, mainly in a L2 academic classroom. The data was collected through (1) a personal narrative which traces each student’s firs-year experience and view toward American oriented classroom participation, and (2) an individual interview to explore in-depth information missing in the narrative accounts. The findings suggest that both Saudi students experienced difficulties and challenges in negotiating competence, identities, and power relations, which was crucial for them to participate and be accepted as legitimate and competent members of their classroom communities. Based on these findings, this paper argues that newcomers’ (i.e., international students) socialization in a certain academic discourse community is conflictual and complex process, which involves struggle, negotiation and construction and deconstruction of identities. Possible implications for instruction are discussed.