Abstract Background Vietnam has a high burden of undetected tuberculosis (TB). The Vietnamese National TB Strategic Plan highlights active case-finding (ACF) as one strategy to find people with TB who are currently unreached by the existing government health services. The IMPACT TB (Implementing proven community-based active TB case-finding intervention) project was implemented across six districts of Ho Chi Minh City, 2017–2019. We aimed to explore the facilitators and barriers for ACF implementation during the IMPACT TB project to understand how and why the intervention achieved high yields. Methods This was an exploratory qualitative study based on 39 semi-structured key-informant interviews with TB patients who were diagnosed through ACF, employees and volunteers who implemented ACF, and leaders from district, national, or international institutions and organizations in Vietnam. Thematic analysis was applied, using an implementation science framework by Grol and Wensing. Results We generated three main themes: (1) the studied ACF model used in Vietnam provided a conducive social and organizational context for ACF implementation with areas for improvement, including communication and awareness-raising, preparation and logistics, data systems and processes, and incentives; (2) employees and volunteers capitalized on their strengths to facilitate ACF implementation, e.g., experience, skills, and communication; and (3) employees and volunteers were in a position to address patient-level barriers to ACF implementation, e.g., stigma, discrimination, and mistrust. These themes covered a variety of facilitators and barriers, which we divided into 17 categories. All categories were mentioned by employees and volunteers, except the category of having a network that facilitates ACF implementation, which was only mentioned by volunteers. This study also highlighted examples and ideas of how to address facilitators and barriers. Conclusions IMPACT TB provided a favorable social and organizational context for ACF implementation. Individual employees and volunteers still determined the success of the project, as they had to be able to capitalize on their own strengths and address patient-level barriers. Volunteers especially used their networks to facilitate ACF. Knowledge of both facilitators and barriers, and how to address them can inform the planning and implementation ACF in Vietnam and similar contexts across low- and middle-income countries worldwide.