The future of individual and societal progress is largely dependent on students' success following completion of K-12 education. For most traditionally aged students, this entails a journey into higher education at colleges and universities. This transition is rife with pitfalls that may lead students to stop out, fail out, or make inadequate progress towards completion -- which further compounds social, psychological, financial, and personal challenges they may be facing. However, the challenges that contribute to these outcomes can be addressed and interventions can be designed to best support students in transition. This dissertation addresses these factors through a thematic literature review, a quantitative analysis of psychological and cognitive factors, and a mixed methods analysis of social experiences and the influence of friends on a myriad of outcomes. These studies are novel in the ways in which they approach measuring academic success, and the attention paid to other facets of a "successful" college experience for students such as the importance of self-regulation skills, mental health, and friendships. The literature review explains the importance of the emerging adulthood developmental period, the critical nature of college degree completion, and the factors involved in supporting student success in the transition from high school to college. Cognitive, psychological, and social factors are all offered as highly impactful and associated theory is explicated to establish the basis for the importance of this work. The first empirical study examines the potential impacts of cognitive functioning (self-regulation) on the psychological outcomes (mental health) and academic success of first-semester college students. Correlation analysis revealed an association and analysis of groups shows that the associations between self-regulation and academic performance are impacted by mental health. The second empirical study uses quantitative and qualitative analyses to explore the impacts of social support on belonging in college, mental health, and academic outcomes. The lived experiences of first-semester college students and their impressions of their experiences with friends, academics, belonging, and mental health are thematically analyzed and reveal themes of the importance of mental health in successfully navigating transition and the importance of friend support in overall perceived college success. The products that comprise this dissertation form a cohesive collection of work through which critical psychological, cognitive, and social factors that influence college student success can be more fully understood and studied in the future. In aggregate, the takeaways of this dissertation are the importance of examining success in the college transition through a multi-faceted lens, keeping in mind the importance of academic success but also considering the myriad of factors that can contribute to it and shape the student's overall experience. [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.]