A number of Mobile-Assisted-Language-Learning (MALL) apps have been developed to enlarge students' vocabulary. However, few studies have discussed the potential to learn words deeply and productively. Therefore, this study evaluated the effectiveness of a mind mapping MALL app as an aid to assist northern Taiwan EFL participants in learning vocabulary. The research questions aimed to examine changes in vocabulary learning outcomes, and the perspectives the participants held regarding the app. Data were collected through tests (pretest, posttest and delayed posttest), visualized vocabulary knowledge mind mappings, and surveys. The posttest results showed the use of the mind mapping MALL app enhanced EFL vocabulary learning (t = 3.68, p<0.05; Cohen's d = 0.81, r = 0.38). In addition, based on the questionnaire responses, experimental participants agreed that not only did the MALL app provide them with a feasible way to move from receptive ways of learning to productive ways of learning, but it also bolstered word consciousness and word retention. Analytical ANCOVA results also verified that learners benefited more from the mind mapping app with respect to learning performance in their delayed posttest (t = 3.45, p<.05; Cohen's d = 0.77, r = 0.36). The findings may be construed as an effective method towards learning foreign words and further exploring the potential of vocabulary learning and MALL.