Children of parents with a mental illness (COPMI) are at increased risk for developing psychiatric disorders, especially when parenting is compromised by multiple risk factors. Due to fragmented services, these families often do not get the support they need. Can coordination between services, as developed in the Preventive Basic Care Management (PBCM) program, improve parenting and prevent child behavioral problems? This randomized controlled clinical trial (RCT) compared the effectiveness of PBCM with a control condition. Ninety-nine outpatients of a community mental health center were randomized to intervention or control. Primary outcomes included parenting quality (assessed by the HOME instrument), parenting skills (parenting skills subscale of FFQ), and parenting stress (PDH). Secondary outcomes are child behavioral problems (SDQ). Outcomes were assessed at baseline and after 9 and 18 months. Effects were analyzed by Repeated Measures Analysis of Variance. Most families were single-parent families belonging to ethnic minorities. The results of the first RCT on effects of PBCM suggest that this intervention is feasible and has a positive effect on parenting skills. There was no evidence for effects on the quality of parenting and parenting stress, nor preventive effects on child behavioral problems. Replication studies in other sites, with more power, including monitoring of the implementation quality and studying a broader palette of child outcomes are needed to confirm the positive effects of PBCM. Long-term prospective studies are needed to investigate if improved parenting skills lead to positive effects in the children in the long run.