The aim of the study was to find out the effect of online vocabulary education on the vocabulary achievement levels of EFL students. It also aimed to reveal the perceptions of EFL students towards the use of online vocabulary education to improve their vocabulary retention. Another aim of the study was to find out the challenges faced by EFL students while receiving online vocabulary education. To this end, the study was conducted as a mix-method study that includes 38 EFL students who were chosen via the convenience sampling strategy. The data of the study were collected through pre-and post-achievement tests, a questionnaire and semi-structured interviews. While the data acquired via pre and post-tests and questionnaires were analyzed by using SPSS 25 Statistical Package, the data obtained through semi-structured interviews were examined by adopting a categorical-content analysis approach. The study results uncovered that providing online vocabulary education is a fertile strategy that can help students improve their vocabulary proficiency. It was also revealed that students managed to learn various words effectively during the online education process, and online vocabulary teaching increased their language learning motivation. The results of the study also showed that in spite of the pros of online vocabulary education, it creates some challenges for EFL students.