The foundation of positive interpersonal relationships is trust and such relationships are needed for professional collaboration and learning to take place. Building trust, then, must be important in order to meet organizational goals and impact student success. The purpose of this survey research was to examine the relationship among teachers' trust in their principals, professional learning community, and student achievement in middle schools. This study conducted a secondary analysis of a portion of the Teachers' Opportunity to Learn (TOTL) survey data. The survey was administered to the population of 896 middle school mathematics teachers in 179 schools in 117 school districts in the State of Missouri. Four research questions were examined using descriptive statistics, correlational analyses, and multiple regression analyses. The results of this study support and expand previous research in finding that there is a relationship between teacher-reported levels of teacher trust in the principal and professional learning community in middle schools. Additional findings recognize the significant effects that school background characteristics can have upon the levels of trust and professional learning community. However, there was no statistically significant relationship between teacher trust in the principal and student achievement nor a mediation effect through professional learning community. Future research is needed to further investigate the possible pathway between teacher trust in the principal and student achievement. In order to combat the academic declines which so often appear in the middle school years, policymakers, school boards, and district administration would be wise to heed the plethora of research surrounding trust in leadership and professional learning communities as an avenue for improving instruction and increasing student achievement in middle schools. [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.]