This study proposed to enhance mobile learning engagement with PACARD (Personalized Adaptive CARD-based interface) that combines several technologies including card-based interface, personalized adaptation, push notifications, and badges. To evaluate our proposal, we distributed a mobile learning application (app) called "English Practice" on the Google Play store, and 63,824 online users were recruited to join the experiment. Six metrics of app engagement (app retention, session length, session count, total time consumption, average duration per day, and uninstall rate) were logged and analyzed. Results are presented in three parts. First, PACARD increased the number of user sessions, duration of use, and retention of app. Second, investigating PACARD also provided detailed reports about users, including their habits and behaviors, thus providing greater understanding of PACARD use. Third, PACARD improved learning achievement. Because of the large number of participants, this study's findings are reliable and widely applicable. PACARD is easy to implement and tailor to most mobile devices and mobile learning apps on the market. Indeed, it benefits educators and mobile app developers as well as learners themselves.