Abstract: Nowadays, the importance of vocabulary in learning English is undeniable. This study was conducted to examine the impact of the use of similar sound techniques on high school students’ English vocabulary competence in a high school in Vietnam. In particular, the objectives of the study were to find out a) the current situation of learning English vocabulary of high school students in a high school in Vietnam, b) difficulties faced by high school students when learning English vocabulary, c) the effect of similar sound techniques on high school students’ English vocabulary competence. Participants in this study were 20 students in grade 11