This study employed a multilevel modeling approach to examine the impact of principal instructional leadership on teacher efficacy and the mediating role played by faculty trust in that process. A total of 50 secondary school principals and 714 teachers in a minority region of Western China participated in the study. The results indicate that instructional leadership, in terms of developing a positive learning climate, directly and positively affects teacher efficacy. Instructional leadership practices that define the school's mission, manage the instructional program, and develop positive school learning climate, positively affect faculty trust. The results underscore the fact that specific instructional leadership practices have more indirect than direct impacts on teacher efficacy through faculty trust in the principal. The areas of significance identified by this study may guide policy makers and practitioners for informed decisions and interventions targeting to build up teacher efficacy.