Mental stress is a serious emerging health issue among higher education students. Time management is often promoted for students as an effective strategy to cope with stress. However, previous research indicated that promoting students' perceived ability to control their times can directly reduce their stress. Based on the results of a large-scale study involving 502 participants, we identified that the ability to be organized is the most effective time management behaviour that promotes students' perceptions about their ability to control their times, reduce stress, hence, anxiety. We applied these results to design a mobile app intervention (called SortOut), which includes seven persuasive strategies implemented as sixcore features. SortOut app aims to help students manage their stress and anxiety by promoting time management via preference for organization and control over time. We evaluated SortOut app on 68 participants, considering possible differences based on gender and degree level. Overall, the results revealed the app was perceived as strongly persuasive and had high motivational appeal. Yet, the app design provoked and sustained females' attention more thanmales. Usability evaluation shows the app is useful and easy to use, hence more likely to be accepted and used. Finally, we conducted a thematic analysis on the participants' feedback and suggestions that will be used to refine the app design.