The purpose of this non-experimental, quantitative study is to investigate the relationship between the use of project-based learning (PBL) by secondary business teachers and time spent in professional development of secondary business teachers for the teaching of 21st century skills. The four identified 21st century skills that will be researched include: (1) critical thinking, (2) collaboration, (3) communication, (4) creativity and innovation. A sample of 316 secondary business teachers were surveyed about their classroom practice and reflection of teaching 21st century skills. This study used a modified version of the 21st Century Teaching and Learning Survey. Survey results were analyzed for relationships using correlational and regression analysis. Business teachers reported a statistically strong relationship between the use of PBL and the teaching of 21st century skills. A statistically significant relationship between time spent in professional development and the teaching of 21st century skills was not found. Regression results indicated that the use of PBL had an impact on the teaching of 21st century skills. This research guides teachers, school administrators, and CTE directors at the state and district level towards the creation of professional development and implementation strategies when applying PBL methods in career and technical education settings. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]