The purpose of this study was to examine the possible effects of the simultaneous inclusion of self and other ratings of principal instructional leadership on teachers' self-efficacy beliefs. Special attention was given to the case where principal and teacher ratings were incongruent and exhibited a self-other rating disagreement regarding the principals' effectiveness in instructional leadership. The data used in the analyses were taken from the Organisation for Economic Co-operation and Development's (OECD's) Teaching and Learning International Survey (TALIS) conducted in 2008 and involved information from 672 principals and 11,323 teachers in four OECD countries located in the broader Asia-Pacific region. The study tested a set of hypotheses based on a multi-source assessment framework for the analysis of leadership performance. Results indicated that principal-teacher incongruence regarding principal instructional leadership was significantly and negatively associated with teacher self-efficacy across all four countries. The findings suggest that multi-source assessment can provide unique performance-relevant information about leadership that would not be captured by traditional single-source ratings alone.