<p>The primary aim of this study is to investigate the impact of a mobile flashcards application, Quizlet, on the students’ performance and autonomy in vocabulary learning. The study also attempts to explore the perceptions of students and their teacher about incorporating this application into the teaching, learning and practicing of target vocabulary in English language preparatory classes. To achieve these objectives, a nonrandomized quasi-experimental research design was adopted. The participants were selected from two intact classes of Turkish EFL students enrolled in a language preparatory program at a foundation (non-profit, private) university in Istanbul, Turkey. The data was collected through pre- and post- vocabulary tests, an online survey, student interviews and a teacher’s reflective journal. The findings revealed that Quizlet had a positive impact on students’ performance and their autonomy in vocabulary learning. The overall perceptions of participating students and their teacher about using Quizlet to teach and learn English vocabulary were also positive. Based on these findings, the study provides practical implications and offers suggestions for integrating mobile learning into English language preparatory classes.</p>