Disclosure, or revealing personal information to others, is important for the development and maintenance of close relationships (Jourard, 1971; Rotenberg, 1995). More recently within developmental psychology, however, the focus has been the study of adolescent disclosure to parents as a means of information management regarding their daily activities. This research assumes that a) disclosure between multiple adolescents and parents within the same family are similar, and b) only information transmitted from adolescents to parents is important for adolescent well-being. Thus, this article presents the findings of 2 within-family studies to investigate differences in the amount and social domain (Smetana, 2006; Turiel, 2002) of youth disclosure to mothers versus siblings, and the influence of disclosure to siblings on relationship quality and youth emotional adjustment. Study 1 utilized 101 sibling dyads with youth ranging in age from 11-21 years, but all siblings living together. Study 2 investigated a sample of 58 sibling dyads in which all first-borns were first-year college students and all second-borns were in high school. All participants completed questionnaire measures to assess study variables. Findings revealed that while youth disclosed more to mothers than siblings, this difference disappears by emerging adulthood, particularly depending on the domain of the issue. Additionally, while greater disclosure among siblings was positive for the quality of the relationship, sibling disclosure was differentially associated with emotional adjustment depending on whether youth were the disclosers or being disclosed to, the domain of the issues disclosed, and the gender composition of the dyad.