Breakdown of foster care has been defined as the situation in which one of the involved parties terminates the intervention before having achieved the goals established for the case plan. This work presents a study carried out with a Spanish sample of 318 closed cases of children who were placed in foster homes and kinship care. The data were collected through the exhaustive review of the child protection and foster placement files, complemented with interviews of the welfare workers in charge of each case. The rate of breakdown of the entire sample was 26.1%, although it was significantly different in kinship care (19.7%) and foster care (31.2%). The results of this study indicate that the variables related to breakdown depend on the placement modality, either in foster care or kinship care. In the first case, the variables related to the child's characteristics are noteworthy, especially behavior and academic problems, with special relevance in the 9-12-year-old group, and in children who were previously in residential care. In contrast, in kinship care, the parents' problems (prison, mental health) and having some measure of guardianship are the most important. The fact of undergoing foster placement after having lived in various residential homes is transcendental. Lastly, the availability of economic resources and even the foster carers' studies seem to be related to foster breakdown.