Mobile language learning has attracted much attention in recent years. Previous research has demonstrated a relationship between perceived usefulness and continuance intention to use technology. This study used a cross-section design to further investigate the possible association between perceived usefulness and continuance intention in the context of language learning and the mediating effects of integrative motivation and flow. A total of 500 college students who were learning English through mobile applications (apps) completed the Perceived Usefulness Scale, Integrative Motivation Scale, Flow Scale, and Continuance Intention Scale. Correlation analysis showed that perceived usefulness, continuance intention, integrative motivation, and flow were significantly positively correlated with each other. Results of regression analysis showed that integrative motivation and flow played multiple mediation roles in the relationship between perceived usefulness and continuance intention. That is: (1) perceived usefulness was positively related to continuance intention toward language learning apps; (2) both integrative motivation and flow played partial and parallel mediating roles between perceived usefulness and intention to use language learning apps; and (3) integrative motivation and flow mediated the relationship between perceived usefulness and continuance intention toward language learning apps sequentially. These results indicated that intention to use language learning apps among language learners can be promoted by way of the increasement of perceived usefulness of these apps, the enhancement of integrative motivation, and the improvement of flow experience. This creates the foundation for apps designers to focus more on inspiring learners to use the social connection functions of the apps, which helps them stay engaged in interactive language learning.