This study aims to identify the risk and protective factors most associated with cognitive/language and socio-emotional development of vulnerable children receiving preventive or protective services. 185 children at Time 1 and 161 children at Time 2 (post-test) were recruited from child preventive and child protective services. Child functioning, family and community environment, and parent–child relationship were evaluated. Bivariate then multivariate analyses were performed based on the results obtained in the initial analyses; a set of multiple regressions formed the basis of path analyses for each of the dependent variables. Data from the second measurement time were used mainly for sample replication. Parental stress and child abuse potential were negatively related to the children’s socio-emotional development. Parental stress was also negatively related to cognitive/language development. The quality of the home environment was positively associated with the children’s cognitive/language and socio-emotional development. Socio-economic risk and social support were not directly associated with outcomes. However, socio-economic risk was inversely related to the quality of the home environment, whereas social support seemed to act as a moderator of child abuse potential and the quality of the home environment. These trends were mostly confirmed at Time 2. The decrease in parental risk factors between Times 1 and 2 was associated with an improvement in socio-emotional development, whereas improvement in the quality of the home environment was associated with better performance in cognitive/language tests. Results suggest the importance of taking action at several systemic levels to improve the development of vulnerable children.