In this study, 116 emerging adults and adolescents completed questionnaires and were interviewed about their relationship with a sibling. Respondents' siblings and their mothers also rated the quality of the sibling relationship. Emerging adults were found to spend less time and to be less involved in joint activities with their siblings than adolescents, but they reported being more involved in emotional exchanges with and feeling more warmth toward their siblings. Conflict and rivalry were also reported by emerging adults to be less intense than by adolescents. Narrative analyses showed that emerging adults had a more mature perception of their relationship with their siblings. Unlike in adolescence, the quality of emerging adults' relationships with their siblings was less related to their relationship with their parents. The results are discussed in the framework of changes in close relationships from adolescence to emerging adulthood.