Emotional and Social Competencies (ESCs) are considered important to school leadership because it is believed that they can help to build trusting relationships with staff and improve organizational capacity within the school. Limited case study research has been conducted on how ESCs are manifested in principal practice. This case study is designed to provide an in-depth description of one elementary school principal's demonstration of emotional and social competencies and their apparent connections to trusting relationships with the staff and improved school organizational capacity. Drawing on literature on school principal leadership, affective dimensions of leadership, trusting relationships in organizations, and organizational capacity, this study uses data from an interview, an open-ended questionnaire, observations, documents, and a survey to provide a descriptive account of how ESCs are evidenced in the leadership practice of one elementary school principal. Overall findings suggest a high correlation between principal ESCs and the trusting relationships necessary to build school capacity. In short, not only are strong principal ESCs, trust, and organizational capacity highly correlated in this school, but there is theoretical reason to suggest causal relationships: if ESCs are conducive to building trust, and trust is conducive to building school capacity, then principal emotional and social competencies are likely to be critical for effective school improvement leadership. This study holds implications for greater attention to ESCs in preparing principals for effective leadership, for principals in practice, and for future research on such issues as how ESCs are best developed in principals and how and why ESCs relate to effective school leadership. [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://www.proquest.com/en-US/products/dissertations/individuals.shtml.]