Vocabulary teaching through tasks has been increasingly popular in teaching English as a foreign language (EFL) in higher education institutions in Asia, includingVietnam. However, vocabulary teaching at high schools is mainly focused on traditional way and, to some extent, this approach is more likely to be seen to prevent students from having opportunities to learn, communicate, and interact with other peers in English. This paper therefore reports on task-based vocabulary teaching by EFL teachers in tenth grade classes and examines their perceptions of this instructional type within a high school context. The study used a pretest-posttest design. Data were collected from two groups of seventy tenth graders at a high school in a Mekong Delta region. The findings indicate that students in the experimental group outperformed those in the control group, suggesting that vocabulary teaching through tasks was useful to tenth graders using the new textbook. The findings also reveal participants’ perceived need for the inclusion of vocabulary through tasks in their learning process. Implications for language teachers and school administrators are also presented.