After finding research confirming that the innovative approach of project-based learning (PBL) improves 21st century education for all students, the administrators of a large local diocesan Catholic school system (LDCSS) initiated PBL implementation in their schools. The problem was that after 6 years it was not known how the teachers were experiencing and perceiving their progress with this implementation in the classrooms. The purpose of this basic qualitative study was to discover and understand LDCSS teachers' experiences and perceptions of their progress of PBL implementation in the classroom. The conceptual framework for the study comprised John Dewey's educational philosophy of experiential learning and Lev Vygotsky's educational philosophy of a constructivist learning environment. Data were collected through person-to-person video interviews with 12 teacher participants in Grades 6-8 from four LDCSS schools. The main research question that guided the teacher interviews focused on understanding those experiences and perceptions of teachers regarding their progress in implementing PBL in the classroom. Data were analyzed through coding to identify themes. Findings indicated that LDCSS teachers' personal and professional knowledge, experiences, beliefs, and professional support affected their experiences and perceptions of their progress of PBL implementation. These findings were used to design a professional development program that may help administrators in Catholic schools know how to support teachers in effectively implementing PBL. Implications are that effective PBL implementation may impact students' learning and preparation for success in their 21st century education, careers, and life, contributing to positive social change. [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.]