Purpose: Little is known about how teachers view the leadership of assistant principals in comparison to that of principals, especially in relationship to teachers' work outcomes. We examine whether a gap exists between teachers' perceptions of fairness from principals and assistant principals, and whether this gap is associated with teachers' commitment to their school. Research Methods: We employ mixed methods with a converging evidence model to understand the relationship between teachers' perception gaps and commitment outcomes. We analyze interview data from 98 teachers across five high schools in one metropolitan area in the U.S. South to describe these gaps, and analyze survey data from 354 teachers from these same schools using structural equation modeling. Findings: Our qualitative analysis uses a typology to show examples of typical work scenarios where a teacher perceives a gap or no gap in fairness. Results from our quantitative data analysis suggest teachers express more commitment when they assess as fair (i.e., unbiased) the performance feedback from assistant principals rather than head principals. Yet, teacher commitment hinges on greater considerate interpersonal treatment from principals than from assistant principals. Overall, gaps in administrator fairness are associated with lower average teacher commitment. Implications for Research and Practice: Our investigation advances understandings of school leadership by clarifying role distinctions between principals and assistant principals that go beyond task types and considering expectations teachers hold of different school administrators. These perception differences matter as they appear associated with levels of teacher commitment.