Considerable research on the two-way Spanish immersion model of education highlights benefits such as biliteracy, high academic achievement in both languages of instruction, and sociocultural competence for students of various linguistic and sociocultural backgrounds. The desire to gain these 21st century skills has caused a proliferation of dual immersion programs across the nation, especially in the state of California. However, most research on dual-immersion programs, such as two-way Spanish immersion programs emphasize English academic achievement outcomes of English learners and English-speaking students, and minimal research describes Spanish outcomes for emergent bilingual students enrolled in these programs. Grounded in the conceptual framework for biliteracy development, which is composed of concepts and tenets gathered from the continua of biliteracy (Hornberger, 2003), culturally relevant pedagogy theory (Ladson-Billings, 1995), culturally sustaining pedagogy theory (Django, 2012), holistic biliteracy framework (Escamilla et. al, 2014), and the translanguaging pedagogy theory (Williams, 1994), the present qualitative phenomenological study aimed to explore how bilingual educators' understanding of biliteracy impacts biliteracy development in two-way Spanish immersion programs. Semi-structured interviews were used to collect data from nine K-8th grade two-way Spanish immersion bilingual educators from the Inland Empire region of California. Two research questions guided this study: 1) How do bilingual educators construct meaning for biliteracy development in two-way Spanish immersion classrooms? and 2) How does their understanding of biliteracy development impact their practice of biliteracy development in two-way Spanish immersion classrooms? Five major themes emerged: 1) educators' cultural identity and experience with bilingualism, 2) educators' preparation to instruct in a two-way Spanish immersion setting, 3) critical areas for Spanish biliteracy development, 4) the impact of teacher professional development on biliteracy instruction, and 5) teaching strategies for biliteracy development. This study brings to light the experiences and understanding of biliteracy development of bilingual educators in two-way Spanish dual-immersion schools. Findings in this study underscore critical factors that impact biliteracy instruction in two-way Spanish immersion programs and promotes a better understanding of the implications of biliteracy development of emergent bilinguals. The lived experiences of participants in this study provide stakeholders such as higher education leaders, district-office administrators, school-site administrators, school-site educators, and researchers an understanding of what type of supports pre-service and in-service educators of bilingual education require to instruct for a more equitable and just education that supports biliteracy development for emergent bilingual students enrolled in two-way Spanish-immersion programs. [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.]