Purpose: How principals hire, assign, evaluate, and provide growth opportunities to teachers likely have major ramifications for teacher effectiveness and student learning. This article reports on the barriers principals encountered when carrying out these functions and variations in the degree to which they identified obstacles and problem-solved to surmount them. Research Methods: I conducted semistructured interviews with 30 principals in charter or conventional schools in two adjacent northeastern states. State A has been at the national forefront of efforts to raise teacher effectiveness. State B is a particularly strong union setting. Charter school principals constituted 23.3% of the sample; 53% of principals worked in urban schools. After coding interview transcripts, I used thematic summaries, categorical matrices, and analytical memos to identify themes across participant experiences. Findings: Principals encountered barriers to cultivating teacher effectiveness that were economic, contractual, cultural, and interpersonal. Principals with more professional development regarding how to improve teachers' instruction and principals of schools that were elementary, smaller, and in State A reported fewer barriers and more opportunities to developing human capital. Implications: Implications for policymakers include creating incentives to draw teachers to urban and rural schools and curtailing teacher assignments that prioritize seniority. Implications for practitioners include efforts to shift the culture of schools to support principals in providing accurate and frank feedback on instruction. Further research should examine whether the patterns identified here hold for a larger, random sample of principals including those in large, urban districts and right-to-work states.