In Vietnamese secondary education, translation and visuals are traditionally used as major techniques in teaching new English lexical items. Responding to the Vietnamese government policy issued in 2008 on using IT for a quality education, the application of PowerPoint has been considered the most prevalent type of technology used in the classrooms throughout in Vietnam as Rickman (2000) stated. This paper reports the impact of implementing PowerPoint in teaching vocabulary in English classes in a Vietnamese secondary education setting. The study, with a two-group pre-test and post-test design aimed to test the effects of PowerPoint on learners' vocabulary retention and to investigate their attitudes towards the use of PowerPoint-based materials in teaching and learning vocabulary. 68 grade 10 students in an upper-secondary school in the Mekong Delta participated in the study. Three instruments were used to collect data: English vocabulary tests, questionnaire on students' perceptions toward the use of PowerPoint, and interview questions on teachers' evaluation of the contributions of PowerPoint to vocabulary teaching and learning. Results indicated that participants in the experimental group outperformed those in the control group in terms of vocabulary retention and their attitudes towards the use of Powerpoint in teaching and learning vocabulary were positive.