Research on higher education institution (HEI) employees neglects an essential group--non-instructional staff. Literature on HEI workers and their salaries focuses primarily on faculty and administrators. Furthermore, the literature that does focus on staff salaries neglects variation within this group as well as the role of institutional and environmental factors in determining staff salaries. Drawing on prior work in higher education and sociology, we address this gap and argue that salaries should vary across institutions and occupations based on institutional context, occupational structure, and environmental factors. Consequently, we analyzed staff salaries at public and private four-year U.S. HEIs (2012-2017) to understand salary variation across institutions and occupational groups. We used multilevel regression models to assess how both overall staff salaries and occupation-specific staff salaries differed within and across institutions, and how they changed over time. Our analyses show that HEIs with more resources, students, staff unions, and elite status pay higher staff salaries compared to others on average. Additionally, there were significant differences in how institutional and environmental factors were related to salaries across different staff occupations. The relationship among institutional context, occupational structure, and environmental factors, and staff salaries is clear, as is the potential for institutional practices that better support this often-overlooked sector of the academic workforce.