This study aimed to investigate the effects of mobile learning on student engagement in high schools, using a mixed-methods design and conducting the study in three different high schools in Vietnam. A total of 130 high school students participated in this study. The findings revealed that students who utilized mobile learning reported significantly higher levels of engagement and motivation, as well as an improved sense of autonomy in their learning process. Furthermore, the study showed that mobile learning can promote active learning, as students were able to access and interact with learning materials outside of the classroom. Additionally, the study highlighted the challenges that come with implementing mobile learning, including the need for adequate infrastructure and training for teachers. It also emphasized the significance of aligning mobile learning with the curriculum and ensuring that students have the necessary guidance and support to effectively use mobile learning. This study concluded that mobile learning can be an effective approach to improve student engagement in high school education. Nevertheless, proper implementation is crucial in order to overcome challenges and fully leverage the benefits of mobile learning.