Research continues to support the positive link between teacher collective efficacy and student achievement. The purpose of this study was to better understand how principal leadership behaviors affect teacher collective efficacy beliefs. The study was designed around Goddard, Hoy, and Hoy's construct of teacher collective efficacy, which is grounded on Bandura's efficacy constructs. The sequential mixed-methods study was designed to examine the perceptions of teacher participants from one Texas Title I middle school regarding principal leadership behaviors. A case study approach was used to construct meaning from teachers' perceptions about the effects of principal behaviors on teachers' beliefs regarding the components of collective efficacy. The quantitative portion of the study (a survey) examined teacher perceptions of their collective efficacy beliefs regarding various facets of the school organization. The qualitative portion (focus group and individual interviews) centered on what teachers perceive to be the impact of principal leadership behaviors on their teacher collective efficacy. Findings from the quantitative portion of the study suggest that teachers perceive their levels of collective efficacy to be higher when reflecting on factors that are primarily connected to school, like learning, motivating students, and handling student discipline issues. Findings from the qualitative portion of the study suggest that when principals exhibit collaboration, empowerment, relationship building, and trust, teachers perceive the leader to be effective. The study was limited to one Title I middle school so an extension to the study which would include other middle or additional high schools is recommended.