This study aims to examine the perceptions of Vietnamese English as a foreign language (EFL) high school teachers regarding the implementation of the competency-based English teaching curriculum (CETC) in the Mekong Delta region of Vietnam. Utilizing a qualitative approach, this study sought to delve into the challenges high school EFL teachers faced while implementing the CETC in Vietnam. Semi-structured interviews with 10 teachers were conducted to gain insights into their experiences, specifically targeting their perceptions of difficulties and their suggestions for potential solutions derived from these experiences. The findings reveal teachers’ perceptions of their perceived difficulties related to student-related factors (low English proficiency, and limited self-directed learning abilities), teacher-related factors (traditional teaching methods, inadequate language and pedagogical skills, and insufficient training), and institution-related factors (large class sizes, limited teaching time, and inadequate facilities). In addition, the teachers recommended strategic solutions for a better implementation of the CETC including providing constructive feedback, promoting collaborative learning, enhancing teachers’ language and pedagogical proficiency, reducing class sizes, and improving facilities. Accordingly, the study contributes to the understanding of CETC implementation and provides practical implications for teachers, students, and policymakers in Vietnam and other similar contexts.