Social investment does not yet appear to have entered the social work lexicon yet reflects a shift toward early intervention and prevention and policies relating to early childhood education and care across the world. Recently, the prime minister of Australia announced new measures relating to childcare to ease the burden on working families and ensure high-standard care for pre-school children. Also announced was a mental health check to be administered by general practitioners for children as young as three years old. This change in social policy follows closely on the heels of the backlash against ameliorative welfare and move toward the preventive end of the social care spectrum. This paper examines developments leading to the social investment approach. It begins by defining social investment and providing an overview of key theorists contributing to our understanding of what ‘social investment is investing in’ and ends with a discussion of its implications for social work.