This study was conducted at Chu Van An High School to discover high school students’ perceptions of Quizlet application for English vocabulary learning. The aims were to find out how often they use Quizlet, what their attitudes are, and what difficulties they face. The students who took part in this study were all from Chu Van An High School in Hanoi, Vietnam, and were in their final year of study. There were 200 students in total who took part in the study. The students who took part in the questionnaire were chosen based on convenience sampling and the interview students were chosen based on purposive sampling. After the questionnaires and interviews were completed, the data was analyzed descriptively and based on the main themes. It was found that the students frequently used Quizlet when learning vocabulary, especially at school. Moreover, they used Quizlet more than other methods. It was also found that students had positive attitudes towards Quizlet. Their affective and value attitudes were most positive. Furthermore, the students had several difficulties, including internet problems, distractions from ads, and boring modes.