This chapter discusses findings from a 1-year exploratory study of an online teacher professional development (PD) program, and an accompanying digital badge system. Twenty-nine middle and high school history and social studies teachers from 13 states participated in the design-based research (DBR) study. Data include responses to online surveys, back-end activity logs, and interviews. Because the badge system was based on a mastery-based approach to teacher professional development and required a significant time commitment, relatively few participants obtained badges. Most teachers acknowledged the value of the badges as credentials for external audiences, but none received any formal recognition by their schools or districts. All participants saw value in the competency-based approach to professional development, but without some form of external validation, they felt that most teachers would be disinclined to pursue these types of badges. An important finding to emerge from participants’ comments is the idea of using a badge system to structure professional development activities such that they are linked to a discipline-specific system that builds teacher mastery of content and instructional practices. We discuss the findings in the context of using DBR methods to help construct useful credentialing systems. The findings have implications for designing badge systems that offer solutions to complex educational problems.