Young people leaving foster- and residential care more often indicate having mental health problems than their peers from the general population. International research has extensively studied these mental health outcomes of care leavers. However, in Flanders (the Dutch speaking part of Belgium), no previous quantitative studies are known. This longitudinal study explores outcomes of depression, anxiety, sleep and general mental health of care leavers in Flanders and investigates if these outcomes improve in the years after leaving care. Associations with placement factors are explored to support recommendations to the clinical field. The current study involves 175 care-leavers. The participants of the study are between 18 and 27 years old at the start of the study and have all left care. Data was collected using a self-reporting questionnaire touching multiple domains. On all domains, no significant differences between foster- and residential care leavers are found. Residential care leavers more often indicate depressive symptoms than their peers from the general population. Foster care leavers more often indicate sleeping problems. Regarding anxiety, no differences are found. In all conducted analyses, the number of years in care, the age of starting and leaving care, the different types of support during care and whether aftercare was offered were included. However, none of these factors provide a sufficient explanation for the outcomes found. On all scales, the effect of gender, the number of placements and the reason of placement do recur. This indicates the importance of these factors. Policy makers should focus on improving placement stability and extra support for children who were placed due to own emotional or behavioral problems or maltreatment.