High school college advisors have a crucial role in providing college access for underserved students, yet there is little known about how they are prepared and supported in their positions. A multiple case study (Baxter & Jack, 2008) was conducted to examine the varying ecological factors that directly and indirectly impact college advisors' roles within high schools as well as their professional development. The research questions that guided this study were: (1) How do college advisors serving underserved students in high school contexts describe their onboarding and ongoing professional development experiences? (2) How can an ecological framework assist in understanding the factors that shape college advisors' roles within their high school contexts and professional development experiences? (3) How can the narratives of college advisors inform best practices to support them in their roles in facilitating college access for underserved students? The study included six participants who provided varying forms of data including a questionnaire, documents, an individual interview, and focus group. Bronfenbrenner's Ecological Systems Theory (1979) and the Ecology of College Readiness Model (Arnold et al., 2012) served as the foundation for the creation of the framework that guided this study: the Ecological Model of a College Advisor's Professional Development. The study's overarching, thematic findings included: informal training, self-teaching, and learning with the students; all things college related; relationship building & collaboration; advocacy: going above and beyond to assist; barriers college advisors face; and college advisors' need for professional development for advising specific student populations. The factors revealed as influencing the roles and professional development of each of the participants within their high school contexts such as compassion and motivation, kindergarten through twelfth grade school systems, curriculum design, school leader's values, high school's college-going culture reputation, and lack of resources are discussed. Lastly, implications and recommendations based on the study's findings are presented. [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.]