Market-based reforms, such as high-stakes teacher evaluation models aimed at improving teacher instructional practice, have not addressed student achievement concerns, especially among marginalized student demographic groups. Research contends that principal instructional feedback to teachers is a worthy strategy to improve teacher instructional practice, but research does not distinguish high-stakes evaluative feedback from feedback for formative purposes. In addition, conflicting reports regarding teacher receptivity to principal feedback exist. Scant information is available that explains the influence of principal formative feedback on the instruction of teachers. This qualitative study focused on the perceptions and influences of formative feedback reported by teachers who receive feedback from an instructional leader that prioritizes formative feedback as a component of their instructional leadership work. Connected with Perez's (2022) study, thirteen recognized principal instructional leaders committed to formative feedback, spread across three school districts in Washington State, were interviewed. Three focal principals were selected from this group to participate in follow-up interviews to further understand their experiences and commitment to formative feedback. Nine teachers from the focal principals' schools were interviewed to understand how teachers perceive and are influenced by formative feedback. Interview transcripts were analyzed in successive cycles to identify patterns and themes. With regard to teacher perception and reported influences, findings indicate teachers believe formative feedback from their principal is of significant utility in their instructional practice improvement work because it focuses on their growth, contains multiple factors that are specific to their instructional goals, needs, and their students, and promotes and enhances their instructional practice reflection. These findings have implications for research to further describe feedback teachers regard positively and utilize to improve their instructional practice. Implications for policy to move evaluation models towards prioritizing formative feedback also exist. Finally, by considering the findings and recommendations of this study, school organizations can conceptualize a vision for principal professional development to support principals in becoming instructional leaders who prioritize formative feedback for teacher instructional practice improvement. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]