Both principal leadership for professional development and leadership for social justice offer promising but underdeveloped conceptions of professional development content that school principals promote toward teaching for academic excellence and social justice. This article examines the professional learning content promoted by three school principals for social justice. Findings reveal a nuanced understanding of two content strands of professional development: subject matter expertise and social identity development. Principals should promote both strands of professional development to support teaching for social justice and differentiate this professional learning according to teacher needs. Implications for practice, theory, and future research are discussed. (Contains 3 tables and 3 footnotes.)