Abstract Sibling relationships of youth in foster care are often complicated as many youth are separated from their sibling(s) at one point or another. Quantitative studies have identified ways in which sibling placement influences youth outcomes. Fewer qualitative studies have been conducted to understand youth perspectives about their sibling relationships. The purpose of this qualitative study was to examine sibling relationships and sibling separation amongst adults with prior foster care experience. Thematic analysis indicated two overarching themes: ‘Sibling Separation was Common’ and ‘Effects of Sibling Separation’. Each theme was comprised of multiple sub-themes that are discussed in detail and explored through an ambiguous loss lens. Recommendations and implications for supporting sibling relationships for youth in care are provided. Sibling separation is common for youth in foster care. As such, sibling separation is common and can impact youth whilst in care and in adulthood. Understanding sibling separation from the perspective of those who have experienced it provides valuable insight into this phenomenon. Ambiguous loss was used as a framework to help understand why sibling separation can be detrimental for youth in foster care. Results indicate a need for personalised assessments and interventions to support sibling relationships of youth in foster care.