Foster children are at risk for developing disorganized attachment relationships (Van den Dries et al., 2009; Vasileva & Petermann, 2018) and behavioural problems (Goemans et al., 2015; Vanschoonlandt et al., 2012). Video-feedback Intervention to promote Positive Parenting and Sensitive Discipline – Foster Care/Adoption (VIPP-FC/A) is an intervention aimed at improving sensitive parenting in order to promote secure attachment relations and reduce behavioural problems. In this study, a Randomized Controlled Trial (RCT) was used in order to examine the effectiveness of VIPP-FC/A in a Flemish foster care sample ( n = 100), using questionnaires at three measurement moments. The hypothesis was that VIPP-FC/A would increase foster mothers’ sensitive parenting and decrease the externalizing behavioural problems and insecure attachment behaviour of the foster children and parenting stress of the foster mothers. The intervention effects on these four outcome variables were analysed by constructing four multilevel models. After controlling for the baseline measurement, there was no significant main effect of condition for sensitive parenting, externalizing problems, insecure attachment behaviour and parenting stress. There was however a significant effect of condition and age on insecure attachment behaviour: within the group of youngest foster children (under 30 months), children in the intervention group scored lower insecure attachment scores than children in the control group. Additionally, there was a significant effect of condition and type of foster care on externalizing behaviour problems. In the group of children placed in kinship foster care, children in the intervention group had lower external behavior scores than children in the control group.