Research on Task-based Language Teaching (TBLT) has received much attention in language education in Vietnam. However, research on investigating perceptions of secondary school teachers towards TBLT implementation in the Mekong Delta, Vietnam is still scarce. The current study investigates secondary school English as a Foreign Language (EFL) teachers’ understandings of task concept and TBLT principles. It also explores teachers’ attitudes and concerns in implementing TBLT. Ninety-eight secondary school EFL teachers participated in the study. Framed by TBLT principles adapted from Nguyen, Jaspaert and Van den Branden (2018), a survey was used to collect quantitative data. The results indicated that the teachers generally had a high level of understanding of task concept and TBLT principles. In addition, they showed positive views on implementing TBLT in their practices. The results also addressed teachers’ concerns in implementing TBLT into their teaching practices including time constraints, the mismatch between the reform goals proposed by the Ministry of Education and Training (MoET) and current teaching policies at the secondary school level as well as the large class size. Accordingly, insightful implications for a better TBLT implementation in Vietnam and similar contexts elsewhere have been taken into consideration.