This research review examines what is known about the effectiveness of parenting support, and assesses the international evaluation evidence focusing on primary and secondary prevention programmes. It outlines several factors affecting the success of parenting support interventions in terms of service implementation and delivery, as well as outcomes for children and parents. The conclusions highlight the need for more rigorous UK-based evaluations, and for further investigation of the support services for specific parenting groups such as very vulnerable families, fathers, and ethnically diverse families. The review also underlines the need for further national policies that address the broader social inequalities affecting the impact of parenting programmes.