The purpose of this study was to determine factors influencing teacher retention in project-based learning (PBL) schools. Ascertaining these factors and devising a list of best practices could aid both PBL and non-PBL schools in bolstering their schools' teacher retention rates. School administrators could examine the research to extrapolate specific practices that would benefit the unique culture of their schools. This mixed-methods study utilized a survey and interviews to address the two research questions. Themes that emerged from interviews with current PBL teachers were colleague interactions, administrative support, student interactions, autonomy, and motivation. Themes emerging from interviews with PBL school administrators were relationships and autonomy. Last, themes emerging from interviews with former PBL teachers were motivation, student interactions, colleague interactions, and benefits. By examining the themes associated with PBL teacher retention, administrators can devise best practices to positively influence teacher retention within their individual 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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]