In this study, we employed the chain mediation model to examine the associations between teacher-student relationships, resilience, learning engagement, and subjective happiness among left-behind children (LBC). A sample of 431 LBC from southwestern China was assessed at three different time points at six-month intervals. The Subjective Happiness Scale, Teacher-Student Relationship Scale, Connor-Davidson Resilience Scale, and Learning Engagement Questionnaire were utilised for measurement purposes. The findings revealed that the subjective happiness of LBC was influenced by their teacher-student relationships through the separate pathways of resilience and learning engagement. Moreover, the teacher-student relationship could predict LBC's subjective happiness either via a pathway from resilience to learning engagement or through a pathway from learning engagement to resilience. This study underscores the crucial role of teachers in facilitating positive development among LBC and highlights implications for policymakers to prioritise quality training for teachers in rural primary schools. By enhancing childhood teachers' understanding of key factors influencing children's positive development, appropriate strategies can be implemented effectively to support LBC.