Instructional leadership has begun to be examined as an essential factor in school development research. It has received considerable attention, especially in developing countries, in recent years. This study examined the relationship between school principals' instructional leadership and teacher instructional practices and the mediating role of teacher professional learning. A cross-sectional survey design was adopted in the study, and the participants were 385 elementary and middle school teachers working in a city in western Türkiye. The data were analysed through structural equation modelling. Findings demonstrated that instructional leadership significantly predicted teacher instructional practices and teacher professional learning. Findings also highlighted teacher professional learning as a significant mediator between instructional leadership and teacher instructional practices. This study confirmed that instructional leadership can strengthen teacher instructional practice and professional learning in a centralized education system.