Drawn on Looney et al. (2017) framework of teacher assessment identity, this study investigated how EFL university lecturers perceived and developed their assessment identity across six dimensions: knowledge, conceptions, self-efficacy, emotional response, reported practice, and contextual factors. The study surveyed 81 EFL lecturers from seven universities in Viet Nam''s Mekong Delta region. Results revealed that lecturers'' assessment identity is significantly shaped by teaching experience and educational qualifications, with the strongest correlation between teacher confidence and assessment implementation (r= .82). While lecturers demonstrated high competence in communication-focused practices (M= 4.32, SD= 0.59) and strong positive attitudes toward assessment''s instructional value (M = 4.44, SD = 0.61), they showed lower performance in theoretical understanding (M = 3.19, SD = 0.95). Teaching experience emerged as a crucial factor, with experienced teachers (>15 years) showing significantly higher assessment knowledge scores. Institutional context influenced assessment practices, with public sector teachers (80.2%) demonstrating more standardized approaches than their private sector counterparts. These findings contribute to understanding assessment identity development in EFL contexts and provide implications for designing professional development programs that address both technical and psychological aspects of assessment literacy tailored to Vietnamese higher education contexts.