Global Citizenship (GC) has recently claimed its position as desired graduates' attribute in many Higher Education (HE) institutions in different non-Western contexts. However, ambiguity and complexity still linger over what GC means contextually and how this understanding may shape educational outcomes. Taking cognizance of this, a study was carried out to investigate the understanding of GC among Vietnamese HE teachers as major agents in Global Citizenship Education (GCE), in order to discuss their implications for graduate attributes. This study adopted purposeful sampling strategy to conduct in-depth interviews among 14 teachers from 4 different faculties of a private university in Southern Vietnam. Emergent themes were then compared with GC conceptions theorized in the literature. Data analysis revealed a three-fold dimensions in teachers' perception: (1) GC understanding was ambiguous and divergent and uniquely nuanced by personal and contextual factors, (2) triple helix of GC conceptions were intricately entwined in GCE rationales, and (3) GC notion was framed with juxtapositions of conceptions. The findings highlighted an implementation gap in GCE which might subvert the intended educational aim, especially in the context of unavailable official documents to guide GCE. In this way, the paper contributes to the ongoing discussion regarding GCE implementation, and indicates a need to have clearer instructional GCE-related policies and more comprehensive teacher trainings.