Despite attention given to principal preparation program reform, little research exists explaining how candidates develop self-efficacy or how preparation programs contribute to self-efficacy development. Researchers used a mixed-methods study to examine principals' perceptions of program effectiveness, determine underlying constructs related to self-efficacy, explore how those factors functioned, and suggest ways to design program experiences promoting self-efficacy. Results suggest that program experiences should create opportunities for relationship building, authentic leadership experiences working with others, and persevering to build self-efficacy. Faculty can support efficacy development through creating instructional opportunities where students gain mastery of leading others in school improvement strategies, requiring internships of substantial length for relationship development, and designing rigorous coursework and program challenges with supportive structures to teach perseverance.