Academic buoyancy is conceptualised as the capacity to successfully navigate the typical adversities experienced during the course of schooling. Studies have shown positive relations between academic buoyancy and beneficial achievement-related beliefs, emotions, and behaviours. Relations with achievement are often small and studies of reciprocal relations are lacking. In a sample of 1,242 primary school students, we examined reciprocal relations between academic buoyancy, engagement, and achievement. Baseline levels of academic buoyancy and engagement positively predicted subsequent achievement. Achievement predicted gain in academic buoyancy but not engagement. Engagement, but not academic buoyancy, predicted gain in achievement. However, aca-demic buoyancy predicted achievement gain indirectly, mediated through concurrent engagement. Building engagement, academic buoyancy, and foundational mathematics skills, could work synergistically to show downstream benefits for students' achievement.