Background: There have been few evaluations of national area-based interventions. This study evaluated the early effects of Commmunities for Children (CfC) on children and their families and whether the effectiveness differed for more disadvantaged families. Methods: A quasi-experimental cohort study in socioeconomically disadvantaged communities in Australia. Mothers of children aged 2-3 years participated at wave 1; 1488 children in CfC communities and 714 children in comparison communities. Outcome measures included child health and development, family functioning and parenting, and services and community. Results: After controlling for background factors, there were beneficial effects associated with CfC. At wave 3, in CfC areas children had higher receptive vocabulary (mean difference (MD) 0.25, 95% CI -0.02 to 0.51; p=0.07), parents showed less harsh parenting (MD -0.14, 95% CI -0.30 to 0.02; p=0.08) and higher parenting self-efficacy (MD 0.11, 95% CI 0.00 to 0.21; p=0.04). Fewer children living in CfC sites were living in a jobless household (OR 0.56, 95% CI 0.32 to 0.95; p=0.03) but children's physical functioning (MD-0.26, 95% CI-0.53 to 0.00; p=0.05) was worse in CfC sites. For children living in households with mothers with low education there were reduced child injuries requiring medical treatment (MD-0.61, 95% CI-0.07 to-1.13; p=0.03) and increased receptive vocabulary (MD 0.57, 95% CI 0.06 to 1.08; p=0.03). Conclusions: CfC showed some benefits for child receptive vocabulary, parenting and reducing jobless households and two adverse effects. Children living in the most disadvantaged households also benefited.