The study aims at developing EFL vocabulary learning mobile application to enhance students? vocabulary knowledge and retention. The researcher attempted to develop the mobile application based on constructivism theory to learn vocabulary. The application consists 3 parts: Preview, Review 1 and Review 2. The participants were 20 second-year students at Suranaree University of Technology, in Thailand. The application is developed based on Cordova hybrid apps framework and standard web technologies (HTML5, JavaScript and CSS). The vocabulary pretests, post-tests and delayed post-tests, student questionnaires and interviews are employed to collect data. Based on the case study, the results show the constructivism-based vocabulary learning mobile application has positive effects on improving students? vocabulary in terms of vocabulary knowledge and retention; and students express positive opinions towards the implementation of the mobile application. The study concludes with the positive outcomes in further develop the learning application for EFL vocabulary learning.