Over the past two decades, a growing body of research has investigated college students' friendships and how these relationships can both enable and constrain students' success. I review this body of literature, describing the characteristics and processes of college students' friendships. First, I review work that describes characteristics of students' friendships, particularly focused on the roles of similarity and proximity in shaping the friendships students make. Second, I focus on what students do with friends that promote college success. Taking a broad view of success, I focus on how friends facilitate a sense of belonging and identity development as well as specific types of support that students provide, emotionally and academically. Third, I discuss processes related to friendships that impede students from success. I conclude by noting some implications for practice and promising areas of future research on friendships and success for post-secondary students.