The purpose of this mixed-methods case study was to examine the effectiveness of a blended learning community of practice model in providing professional development to improve K-12 teacher's self-efficacy in the implementation of personalized learning. Eighteen teachers participated in a nine-month professional development program focused on personalized learning. Participants took pre and post self-efficacy tests based on nine personalized learning constructs. Qualitative data was collected from feedback surveys, online postings, and individual interviews. Teachers demonstrated greater levels of self-efficacy with regard to the implementation of personalized learning after their participation in the professional development community. They reported increased confidence with regard to personalized learning in the areas of planning, risk-taking, implementation, continuous improvement, and sharing their knowledge with others. Teachers developed additional competencies such as an increased knowledge of their students and skills related to technology, design, problem-solving, and facilitation. Teachers developed new dispositions such as flexibility and open-mindedness. Teachers found that elements of personalized learning could be implemented without technology, but recommended the integration of technology to effectively implement personalized learning across all nine constructs. The online components of the blended design, enhanced the teachers' sense of community and helped to facilitate collaborative, interdisciplinary work.