This paper examines the relationship between gratitude and academic engagement among Chinese high school students, exploring the mediating effects of internal locus of control and subjective well-being. The students of some high schools in Guangzhou were surveyed using the Gratitude Questionnaire-6, the School Engagement Questionnaire, the Levenson’s IPC Scale, and the General Well-being Schedule, and 708 valid questionnaires were collected. Results showed a significant positive relationship between gratitude and academic engagement; internal locus of control and subjective well-being played a mediating role between gratitude and academic engagement, respectively; internal locus of control and subjective well-being played a chain mediating role between gratitude and academic engagement. These findings suggest that we can promote students' academic engagement not only by cultivating their gratitude, but also by improving their internal locus of control and subjective well-being.