Almost seventy percent of today's jobs require postsecondary education or training (Carnevale, Garcia, & Campbell, 2019) and to meet those workforce needs, the United States will need to dramatically increase degree production (Grawe, 2017). However, "beginning in the mid-2020s many colleges will enter an extended period of shrinking enrollment pools" as the numbers of high school graduates are expected to decline (Grawe, 2018, p. 14). Thirty-two of the 50 U.S. states cannot meet educational attainment goals by having only traditional-aged students gain in earning postsecondary degrees (Council for Adult and Experiential Learning, 2008). As the enrollments of "traditional" students on college campuses decrease, policymakers and campus leaders need to recognize and adjust to this change (Falk & Blaylock, 2010).There are individuals who may be enrolled in or want to return to higher education, including "nontraditional students," "post-traditional learners," "today's students," students who work a significant number of hours, those who have stopped out from college, adult students, and part-time students. Students who enroll on a part-time basis are projected to outpace the enrollment of full-time students and make up to 40 percent of college students by 2023 (Hussar & Bailey, 2016). However, since 1970, the overall proportion of part-time students enrolled at public universities has decreased (Snyder, de Brey, & Dillow, 2016). Even though research universities "educate the plurality of our nation's undergraduates" (Owens-Smith, 2018), exclusively part-time students are significantly less likely than their full-time counterparts to attend public or private 4-year doctoral institutions -- 11% versus 33% (Chen & Carroll, 2007). This qualitative case study explored the experiences of part-time undergraduate students in a 4-year doctoral level public institution. "Increased institutional rates of student success are the result of a series of intentional institutional actions, policies, and practices" (Tinto & Pusser, 2006, p.16), but existing research is lacking regarding how policies and practices can encourage persistence and degree attainment for part-time undergraduates (Cooper, 2015). This began to address that gap, with findings that make an important contribution to the literature on higher education policy by focusing on part-time undergraduate students in a public doctoral level university. Supportive policies and practices include: degree programs designed for these students, favorable transfer-in policies, online programs and courses, flexibility, affordability, financial support, positive experiences in the institution, encouraging faculty, accommodating advisors/single points of contact, positive interactions with other academic and student support personnel, and encouragement from other individuals in the students' lives. Barriers to part-time undergraduates' success were due to lack of financial aid, assumptions of full-time enrollment within the advising process, academic program designs, price of college and the cost/benefit of services, a tuition surcharge policy, course mode of delivery limitations, difficulty with transfer-in policies, internship/practicum requirements, negative or non-responsive "front door" interactions, the feeling of a "stigma" especially due to policies and practices, lack of desirable opportunities to engage more with the campus, lack of course availability, difficulty with group work, lack of on-campus parking, and for some, difficult advising experiences. In the final chapter, a Research to Practice Report recommends nine "Key Action Areas" for policymakers and practitioners to improve persistence and success for part-time undergraduates. These include: better data and data analyses, the use of "student portraits," reform of financial assistance options, evaluation of state funding models and tuition and fee charges, reconsideration of academic programs, training for faculty and advisors, designing new engagement opportunities, and recognizing in campus trainings and communications that all faculty and staff can positively influence the experiences of part-time undergraduates. [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.]