Using a sibling design, this study examined the association between adolescents' friendship experiences and their aspirations for self-acceptance, affiliation, and financial success. We hypothesized that adolescent siblings would differ in their aspirations and that unique experiences in friendships would be associated with these differences. Within our sample of 102 same-sex sibling pairs (mean age older sibling 16 years, younger sibling 14 years), only a small degree of sibling similarity was found for aspirations as well as friendship experiences. Self-acceptance and affiliation were positively linked to general friendship positivity as well as to positive features of the adolescents' closest friend. Bivariate model-fitting techniques revealed that nonshared processes (i.e., unique to each child in the family) explained these links between friendship experiences and aspirations. The results indicate that growing up in one home and being socialized by the same parents does not make adolescent siblings similar in their aspirations but rather that nonshared experiences like those with close friends are related to aspiration dissimilarity of siblings. (Contains 4 tables and 3 figures.)