Although decades of research attest to the importance of vocabulary teaching and learning, and recent research points to principles of effective vocabulary instruction, the small number of studies on actual classroom practice suggest that teachers continue to use the least effective approaches, often focusing on memorization of definitions. Research suggests that high-quality vocabulary instruction is multifaceted, including four components as described by Graves (2016): 1) providing rich and varied language experiences; 2) teaching individual words; 3) teaching word-learning strategies; and 4) fostering word consciousness. This dissertation research explored multifaceted vocabulary instruction in one 10th grade English classroom. Using a self-study design and action research methodology, qualitative data were collected over 14 weeks in an effort to shed light on the instructional change process. Findings were analyzed using Graves? four components as well as three theoretical lenses: 1) the metalinguistic complexity of word learning; 2) situated-sociocultural theory; and 3) culturally relevant pedagogy. Themes related to multifaceted vocabulary instruction include: word consciousness as a frame for word learning, academic vocabulary as the focus of individual word learning, fostering student agency to build vocabulary, and my paradigm shift. Additional themes related to the instructional change process focus on teacher knowledge, beliefs, and practice. Implications for teaching practice, teacher professional development, teacher preparation, policy, and future research are discussed. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]