Numerous publications have asserted that placement instability in out-of-home-care is detrimental to the well-being of the children and adolescents experience it. Despite this there has been no systematic review of placement instability on the well-being and development of children in care. To redress this, a scoping search of literature related to placement instability was undertaken, identifying publications which focused on outcomes. Two narrative reviews were conducted; one of longitudinal quantitative data, and the other of qualitative data. The review of qualitative research suggested that young people with experience of placement instability consistently identified a range of adverse outcomes, such as a diminished capacity for trust and close interpersonal relationships. Only one longitudinal study provided strong evidence of a directional effect of placement instability on the well-being of pre-schoolers over time. Several methodological and analytical issues across the wider body of studies prevent their findings from being interpreted with confidence. The issues with the wider body of research in this area are examined, and suggestions are made for future high-quality research.