Despite their importance to the research enterprise, doctoral students are an underexamined population in higher education. Several studies have emphasized the importance of psychosocial characteristics in academic success and scholarly identity formation. However, few studies have explored their developmental trajectories across a range of disciplines to give an overall perspective of the scholarly identity formation process and its nuances. We argue that doctoral education is a socialization process that, if successful, helps doctoral students to develop a disciplinary identity. We propose that this identity development process is mediated by how students internalize their socialization experiences. Therefore, we integrate concepts from self-determination and identity development theory into socialization theory. Using a three-year longitudinal sample at a single institution (n = 1264), we identify doctoral students' developmental trajectories in perceptions of competence, autonomy, relatedness, knowledge, and recognition. We identify six different developmental groups according to baseline levels and developmental trajectories during the first two years of doctoral studies. Further, we find that sex, family income background, and anticipatory socialization experiences are associated with membership in these groups. Lastly, we observe that these trajectories are associated with socialization outcomes. Findings highlight a non-monolithic socialization process that calls for a systematic approach to measure these psychosocial characteristics over time. Implications for theory, research, and practice are discussed.