Purpose: New teacher evaluation systems have expanded the role of principals as instructional leaders, but little is known about principals' ability to promote teacher development through the evaluation process. We conducted a case study of principals' perspectives on evaluation and their experiences implementing observation and feedback cycles to better understand whether principals feel as though they are able to promote teacher development as evaluators. Research Method: We conducted interviews with a stratified random sample of 24 principals in an urban district that recently implemented major reforms to its teacher evaluation system. We analyzed these interviews by drafting thematic summaries, coding interview transcripts, creating data-analytic matrices, and writing analytic memos. Findings: We found that the evaluation reforms provided a common framework and language that helped facilitate principals' feedback conversations with teachers. However, we also found that tasking principals with primary responsibility for conducting evaluations resulted in a variety of unintended consequences which undercut the quality of evaluation feedback they provided. We analyze five broad solutions to these challenges: strategically targeting evaluations, reducing operational responsibilities, providing principal training, hiring instructional coaches, and developing peer evaluation systems. Implications: The quality of feedback teachers receive through the evaluation process depends critically on the time and training evaluators have to provide individualized and actionable feedback. Districts that task principals with primary responsibility for conducting observation and feedback cycles must attend to the many implementation challenges associated with this approach in order for next-generation evaluation systems to successfully promote teacher development.