This dissertation was conducted using case study methodology to examine how teachers of different content areas integrate media literacy into their instruction to address the specialized knowledge and discourses of their disciplines after participating in a media literacy online professional development, how they applied the content from the online professional development to design media literacy instruction, and the changes in their perceived competency with the instructional integration of media literacy as well as their own media literacy while participating in a media literacy online professional development. Findings indicated that teachers incorporated media literacy strategies and concepts to privilege knowledge, ways of making meaning, and discourses specific to their disciplines. They applied content from the online professional development to build background knowledge, offer explicit media literacy instruction, give students opportunities to apply media literacy strategies, and incorporate media creation to demonstrate student learning. They perceived their media literacy instructional and personal competency changed with critical consumption but not with creating or publishing media. Recommendations include implementing a disciplinary media literacy framework to design and deliver instruction, refining the online professional development, and leveraging media literacy concepts for teaching advocacy and social justice as well as teachers' own online civic engagement. [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.]