This study examined the impact of blended learning professional development on the self-efficacy of elementary mathematics teachers. The professional development was delivered through a blended approach and comprised two components. The first was an online course that translated research on mindset, blended learning instructional models, and the use of instructional technology into practical teaching ideas. Delivered asynchronously through the district's learning management system, Schoology, the course was divided into four modules for each of the four blended learning teacher domains. Each module was designed to take approximately 60 minutes to complete over the course of about a week to allow for application and reflection time before moving on to the following module. The andragogy of the course was built around the principle of active engagement and thus included short instructional videos, close reading, discussion/reflection elements, lesson designing tasks. Another component of the professional development was weekly, peer instructional coaching. Cumulatively, the results of the study provide evidence of teacher self-efficacy growth as a result of participation in the blended learning professional development. Implications of the study include evidence to support district leadership in providing professional development to support elementary teachers' self-efficacy in technology-rich teaching and learning environments. [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.]