This qualitative case study conducted under the informed exploration phase of design-based research explored the design process of an online teacher professional development (OTPD) prototype course for Korean language teachers to adopt a multiliteracies-based pedagogy in the K-12 context. This study is a response to the lack of research on professional development entailing the adoption of a multiliteracies-based pedagogy within the K-12 foreign language field that reflects the voices of practicing teachers. The first research question addressed how the designer's experience and design principles were constructed in designing OTPD for Korean language teachers' adoption of a multiliteracies pedagogy. The second research question examined how the participating Korean language teachers experienced and perceived a multiliteracies pedagogy approach during the design process of OTPD. The qualitative case study research analyzed qualitative data, which encompassed interviews with participating teachers, their participation in the sample activities and design document review, as well as the designer's notes and design documents. The designer's experience during the design process is summarized in six generated themes that affected the designer's decisions from initial to revised design--considering students, making real-world connections, and acknowledging the boundaries of the curriculum and program--and from revised to final design--adapting to gradual change and the coexistence of pedagogies, developing a collaboration space for authentic texts for the new pedagogy, and demonstrating practical leading for modeling instructional languages and providing feedback. Subsequently, 12 design principles were generated to guide the design of OTPD, specifically for the adoption of a multiliteracies pedagogy. During the design process, the participating teachers displayed positive perceptions of authentic texts and a multiliteracies-based pedagogy. Nonetheless, they also indicated their need for mutual and practical advice concerning text searching, task scaffolding, and instructional examples and expressed concerns about aligning multiliteracies with their curriculum goals and students' language proficiency. The study's findings confirm the Community of Inquiry framework and provide additional design considerations, thus contributing to the existing knowledge base concerning online design aimed at developing teachers' professional learning for the adoption of a multiliteracies pedagogy. The findings also clarify Korean teachers' practical needs when adopting a multiliteracies pedagogy and identify areas for further research on a multiliteracies-based pedagogy for Korean language teaching. [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.]