This study investigated secondary school teacher's experiences in learning to teach 21st Century skills through the design and implementation of Project based (PBL) curriculum. Data collection focused on in-service teachers who completed a 3-unit, 16-week course part of a Master's degree program in Curriculum & Instruction (C & I). Data were collected through two pre-post surveys--one measuring knowledge and the other measuring teachers' confidence in integrating PBL units into the curriculum, and post course interviews. Results revealed that using PBL as an integrated teaching and learning strategy in the preparation of teachers can develop the self-efficacy required to support the curricular demands necessary to address the learning needs of students for the 21st Century. A sustained focus on pedagogy, curriculum, and skill acquisition is critical to developing 21st-century teaching skills. Implications for teacher learning and the importance of engaging teachers in a professional development experience that integrates college and career readiness curricula and PBL methods are also discussed.