Research shows that students with mild to moderate intellectual disabilities (MMID) transition to post-secondary educational environments and the real-world experience more barriers than their typical peers (Banks, 2014). However, limited research includes the voices of students with MMID and their parents/guardians as they describe their transition from high school to post-secondary lives. This qualitative phenomenological study examined the postsecondary transition experiences from high school into post-secondary settings of students with MMID and parents/guardians who supported students with MMID in the transition process. This study also explored the role of the Individual Transition Plan (ITP) in secondary educational settings, support and resources, self-determination, student advocacy, and post-secondary experiences of students with MMIDs. Two frameworks served as the foundation for this study, exploring how students with MMID develop self-advocacy and self-determination: Kohler and Field's (2003) "Taxonomy for Transition Programing Framework" and Test et al. (2005) framework of "Self-Advocacy for Students with Disabilities." Participants in this study included ten young adults with MMID and ten parents/guardians of young adults with MMID. Participants described their roles, supports, and self-advocacy through semi-structured interviews during the ITP process and the transition between high school, community college, trade school programs, and post-secondary life. Findings suggest that the ITP process and support during high school could significantly impact the student success of young adults with mild to moderate disabilities in their post-secondary lives. In some cases, participants who participated in community-based instruction (CBI) programs were equipped with the necessary skills to survive at home and in the community. Many student and parent/guardian participants described the positive support they received from teachers during the high school transition process. However, not all participants felt they received support from key stakeholders or could express their voice and self-advocacy during the process. These findings point to implications for policy and practice for special education teachers, administrators, colleges, and universities around the ITP and post-secondary transition process for students with MMID. Further research is recommended to broaden the area and location of the study to have a more distinct view of the challenges posed to young adults with ID transitioning from colleges to universities. [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.]