In this article, I argue that Ph.D. students' construction of academic identity depends on the boundary-making process in academia. The presented ethnographic account of Ph.D. students at one of the research-intensive universities in Turkey is based on 15 months of fieldwork, including observations and 21 in-depth interviews with PhD students. This ethnographic study employs a two-headed approach: institution-based boundary-formation and Ph.D. students' socialisation into academic habitus. The findings reveal that, first, the identity building process in doctoral education is constituted by the practices of institution-based boundaries, which enable Ph.D. students to accumulate symbolic and social capital; second, the practices of distinction through socialisation into academic life are developed, embodied, habituated, and integrated to academic identity and academic life as part of a habitus of doctoral education; third, identity formation is a social space of relational positions characterised by the supervisor-enforced social order, rooted in both authority and domination.