This study examined the effect of the inclusive leadership of school principals on teachers’ helping behavior and work engagement and analyzed the mediating role of teachers’ psychological safety. A questionnaire was employed to collect the opinions of junior high school teachers in Taiwan. The data were collected from raters selected through stratified random sampling. The questionnaire comprised two sections. The antecedent (principals’ inclusive leadership) and mediating (teachers’ psychological safety) variables were measured in the first section, whereas items on the outcome variables (teachers’ helping behavior and work engagement) constituted the second section. To analyze the data thoroughly, we examined the validity of the measures of principals’ inclusive leadership, teachers’ psychological safety, teachers’ helping behavior, and teachers’ work engagement by using confirmatory factor analysis. To determine the cross-level effect of leaders’ inclusive leadership within the organizational context on teachers’ helping behavior and work engagement within the individual context, we employed partial least squares–structural equation modeling to examine the relationships between variables as well as the mediating effect of psychological safety. The conclusions of this study are outlined as follows: (a) Principals’ inclusive leadership has a positive effect on teachers’ helping behavior, (b) Principals’ inclusive leadership has a positive effect on teachers’ work engagement, (c) Teachers’ psychological safety has a mediating effect between principals’ inclusive leadership and teachers’ helping behavior, and (d) Teachers’ psychological safety has a mediating effect between principals’ inclusive leadership and teachers’ work engagement. The contributions of this study include further exploration of the mediating effect of psychological safety on teachers’ helping behavior and work engagement as well as the construction of a comprehensive empirical model of principals’ inclusive leadership. Finally, based on the results of the study, practical references and implications for strengthening and improving principals’ leadership, teachers’ helping behavior, and teachers’ work engagement are provided.