Worldwide, the majority of youth reside in low- and middle-income countries (LMIC). School-based mental health (SBMH) services are particularly important in LMIC, in part because of LMIC's limited mental health infrastructure. Among the challenges to developing SBMH in LMIC are limited implementation science (IS) capacity, critical for identifying barriers to evidence-based intervention (EBI) use and dissemination, etc., specific to the local country context. A key step in IS capacity development is conducting a needs assessment, to identify barriers (and their solutions) to IS development itself within the local context. The present study conducted an IS needs assessment focused on SBMH in the Southeast Asian LMIC of Vietnam. Seventy-five Vietnamese mental health professionals in SBMH-related fields participated in a mixed-methods study. Vietnamese SBMH researchers and practitioners most likely to have experience and/or interest in IS were selected for study recruitment. Professionals' formal understanding of and experience with IS as a scientific field was highly limited. However, after reading a brief but detailed description of IS, participants' interest in IS training was high, and their mean rating of its potential utility for Vietnam to develop SBMH was 4.7 on a 1-5 scale. Participants also reported on barriers and potential solutions for EBI use in SBMH in Vietnam. Contrary to expectations, the most frequent and severe barriers were not financial but related to limited stakeholder engagement. Overall, these and other study results provide some suggestions how IS capacity to support SBMH may be most efficiently developed in settings such as Vietnam.