L2 learner engagement is an emerging but critical construct in the field of psychology of language learning and teaching. However, research on L2 learner engagement has suffered from the inconsistent operationalization of the multidimensional structure of the construct and the conceptual overlap among its different components, making research synthesis and comparison across studies and contexts challenging. This study tested the utility of the bi-factor exploratory structural equation modelling framework (B-ESEM)--an overarching psychometric framework that can address the two critical concerns associated with the operationalization and measurement of L2 learner engagement. Data were collected from 413 Vietnamese EFL students. Through two stages of rigorous and strategic data analysis, the results suggested that participants' responses to the L2 learner engagement scale could be best represented by a B-ESEM model that simultaneously assessed the global L2 engagement factor along with the specific components of behavioural, cognitive, affective, and social engagement while, at the same time, controlling for the cross-loadings of items onto non-target factors. Results of the study were discussed from both psychometric and substantive perspectives and implications were provided to capitalize on the utility of the B-ESEM approach in the assessment of L2 learner engagement.