Mobile app engagement is receiving increasing attention in both practice and academic research. The aim of this study was to examine structural relationships through a comprehensive engagement model, and to measure the factors that influence mobile app engagement and loyalty and that match actual purchase history (behavior) data. The study was conducted on the mobile apps of members of a grocery company. The model was used to show that the design of the mobile app (especially its ease of use) increased engagement, and that this engagement influenced attitudinal loyalty (mainly the intention to recommend the app to others) and behavioral loyalty, and positively influenced purchase behavior. Especially, the mobile app engagement had a stronger influence than attitudinal loyalty on actual purchase behavior.