This research focuses on vocabulary acquisition in foreign language learning. The latest trends of teaching as well as the huge advance of technology allow teachers to utilize online and mobile applications through diverse apps. This quasi-experimental design research investigated Quizlet, in its mobile version, on vocabulary acquisition in English as a Foreign Language (EFL). One group of A2 (according to the Common European Framework of Reference for Languages) EFL learners at a state secondary school in Valencia (Spain) (N=24) participated in this study. Learners from the Treatment group (henceforth, T-group) underwent a pre-test and a post-test to assess their acquisition of the assigned vocabulary lessons which were extracted from the course syllabus. After utilizing Quizlet for vocabulary learning for the academic year 2017-2018, the results proved that these learners improved significantly their level of EFL vocabulary at the post-test. Accordingly, this research recommends utilizing Quizlet in its mobile version at secondary education. [For the complete proceedings, see ED600837.]