This paper explores findings from an exploratory study on sibling relationships following adoption reunion in adulthood. The qualitative data was gathered through in‐depth interviews with 33 adopted adults who were reunited with their birth sibling(s) through an adoption agency in the Republic of Ireland. The findings throw light upon the development of the emotional, often complex, relationships which may emerge when siblings meet for the first time in adult life. Factors influential in facilitating or hindering these post‐reunion relationships are discussed. The important insights are then considered in the context of the wider international literature on adoption, search and reunion.