Project-based Language Learning (PBLL) provides students with opportunities to use the target language purposefully and to interact with culturally authentic materials. Because PBLL holds critical benefits for its students, it is important that teachers learn best practices for implementation and how to overcome the challenges that PBLL brings. This study focuses on the experiences of 15 world language teachers as they participated in a PBLL professional development series developed by the National Foreign Language Resource Center (NFLRC) at the University of Hawai'i at Mānoa. Findings from this study are based on data gathered from surveys and interviews with a diverse group of educators for the purpose of gaining an understanding of what participants learned and the activities that impacted learning of PBLL. Results show that learning about gold standard elements of PBLL made the biggest impact on participants' pedagogical beliefs and motivated them to change their practice. Activities that positively impacted learning were those that were active, social, and related to practice. Participants were overwhelmed with the amount of content and needed help making connections between the content and their teaching contexts. Overall, participants' experiences in the professional development series led to a change in pedagogical beliefs and a desire to alter their implementation of PBLL.