Effectiveness in education is a national concern and reform efforts continue to be championed with the hope of stimulating improvement to more effectively meet the needs of all students. Many reform efforts include a focus on teacher professional development to strengthen teacher pedagogy and positively impact student achievement. Rapid expansion and increased use of technology have created opportunities that never existed before to support teachers. Online, as an alternative to traditional face-to-face professional development, is currently underutilized in K-12 school districts. This study intended to investigate successful models of online professional development to inform district decision-making at the local level. K-12 teachers from fifteen states, who participated in a successful online professional development experience, were invited to complete a survey to provide insight about how a professional development experience positively impacted their teaching, learning, and classroom. Of the 328 teachers who responded, three people were interviewed to learn more about their particular online professional development experience. Study findings show that participants highly value online professional development because of the convenience, accessibility, and ability to self-pace and differentiate learning. Online professional development has the unique potential to foster reflection, deep thought, and analysis particularly when there is the potential to interact with an online professional learning community over time. A significant finding is that teachers thrive on the interaction and sharing of ideas between colleagues in job-alike situations. Additionally, findings show that when teachers participate with face-to-face school or grade-level teams online, they reap even greater learning benefits. The majority of participants found that online professional development helped them improve their knowledge of curriculum and instructional strategies and improved their technology skills. They learned ways to improve their classrooms to meet the needs of diverse student populations and helped validate effective practices that were already firmly in place. Educational leaders should consider online professional development as a strong viable option to improve teacher practice. Findings suggest that district leaders should recommend State Department of Education and commercial online learning opportunities that are subject-area focused and aligned to district/school goals. They should encourage teacher teams to participate together online and face-to-face to deepen learning. By recommending specific online learning experiences and encouraging teachers to participate together, districts will be well served by the effective online professional development offerings that are available. [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/en-US/products/dissertations/individuals.shtml.]