In this study we bring together Argyris and Schön's theories of interpersonal effectiveness and research on negotiation to develop a model of effective leadership behavior in conversations involving actual or anticipated disagreement. A concurrent mixed-methods design was used to assess shifts in how 18 Australian superintendents responded to disagreement that arose in conversations about performance problems. The intervention included discussion of the model and its application to participants' own practice through analysis of transcripts, modeling, coaching, and feedback. Assessments of conversation skills and outcomes showed moderate to large intervention effects. The implications for leadership development and double-loop learning are discussed.