This study tested a moderated mediation model of instructional leadership's effects on differentiated instruction, with teacher enthusiasm as the mediator and power distance perceptions of teachers as the moderator. Using survey data from a sample of 772 teachers working at 55 secondary schools, the study performed multilevel structural equation modelling (MSEM) with Bayesian estimation to examine the structural relationships between principal instructional leadership, power distance, teacher enthusiasm, and differentiated instruction. Results replicated the previously established evidence that principal instructional leadership has indirect effects on differentiated instruction through promoting teacher enthusiasm. This study also extends the literature by bringing evidence that the effect of instructional leadership on teacher enthusiasm and differentiated practice is contingent upon the level of power distance in the relationships between teachers and principals. Key implications for policy and practice are discussed.