In the context of educational decentralisation, school leadership encompassing different sources of leadership is significant for school performance. However, few studies have investigated the pathway regarding how principals and teachers as distinct sources of learning-centred leadership exert impact on teacher learning. To this end, survey data collected from 1340 junior high school teachers in Taiwan were analysed with structural equation modelling. The results suggest that both principal leadership and teacher leadership affect teacher learning through direct pathways, and that of teachers exhibits an even greater impact. In addition, principal leadership affects teacher learning through indirect pathways mediated by teacher leadership. By further investigating the mediating effects of different practices of teacher leadership, we found that teacher-led improvement of curriculum and instruction is a critical mediator for teacher learning.