This study investigates the relationship between Chinese students' intentions to learn English and their actual learning behaviors, emphasizing the mediating role of attitude and the moderating influence of institutional support. This research aims to (i) investigate whether students' learning behaviors are directly influenced by their intention, (ii) explore the mediating function of attitude, and (iii) evaluate how institutional support reinforces the intention-behavior relationship. Data were gathered from 388 students at five universities in Jiangxi Province, China, using structured questionnaires that were informed by the Theory of Planned Behavior. Constructs were identified using exploratory factor analysis (EFA), and hypotheses were tested using structural equation modeling (SEM). The findings indicate that students' intentions to learn English have a substantial positive effect on both their learning behavior and attitude. The study found that attitude (indirect impact = 0.249, p < 0.05) partially mediates the association between intention and learning behavior, indicating that an optimistic outlook can improve the conversion of learning intentions into actual behaviors. In particular, this effect shows that pupils are learning more frequently and in more depth. Additionally, institutional support was identified as a significant moderator, amplifying the impact of intention on learning behavior by fostering a conducive educational environment. This research contributes to the existing literature by highlighting the importance of both psychological and contextual factors in language learning. It underscores the necessity for educators and policymakers to create supportive environments that enhance students' motivations and engagement with the English language. By fostering positive attitudes and providing adequate institutional resources, educational institutions can significantly influence students' English language proficiency. The insights gained from this study can inform curriculum development and teaching strategies aimed at improving language learning outcomes in China.