Knowledge about determinants of child and adolescent enrolment in psychosocial care concerns only single types of care and usually only socio-demographic factors. The social environment is also a likely key determinant but evidence is lacking. The aim of this study was to examine the associations between family social support, parenting skills and child and adolescent enrolment in psychosocial care. We obtained data on 1,331 children (response rate 56.6 %), 4-18 years old, enrolled in preventive child health care, and child and adolescent social care and mental health care because of psychosocial problems, and on 463 children (response rate 70.3 %) not enrolled in psychosocial care. Results showed that enrolment in psychosocial care was associated with low family social support (odds ratio; 95 %-confidence interval: 3.2; 2.4-4.4), and with poor parenting skills, i.e. poor supervision (1.5; 1.1-2.1) and inconsistent disciplining (1.5; 1.1-2.1). Children's psychosocial problems partially mediated the associations with family social support and completely with parenting skills. Children's problems did not moderate the associations. Positive parenting was not associated with care enrolment. We conclude that low family social support and poor parenting are important factors associated with enrolment, in particular because they are associated with more frequent occurrence of children's psychosocial problems. This implies that professionals and policymakers need to be aware that factors in children's social environment are related with enrolment in psychosocial care, in addition to children's psychosocial problems.