Since the beginning of the 21ˢᵗ century, social investment has fuelled many Welfare state reforms at the international level. This notion offers a third way between the Keynesian paradigm and the neoliberal approaches advocating the dismantling of social policies. In fact, it distinguishes itself from social protection, focusing on risk prevention rather than compensation. It also enhances social expenditure considering it generates positive social and economic benefits if it aims to support human capital and capabilities in order to develop skills, employability and autonomy. Therefore, it promotes direct programs and actions towards childhood, youth, and occupational integration. This paper aims to shed light on the spreading and implementation of social investment in multi-level governance systems. Therefore, it examines national and subnational territories’ contribution to its deployment, using the example of the 2018 French Poverty Plan called “Stratégie nationale de prévention et de lutte contre la pauvreté (SNPLP)”. The analysis is based on a documentary survey and an interview campaign with 164 stakeholders conducted at the national level, as well as in 6 regions and 13 departments. The article contains two parts. On the one hand, we document the declination of social investment in national territories and show its recent development in France through the Poverty Plan. On the other hand, we look at subnational territories’ mobilization in the dissemination of this perspective through the same Plan. Three main results stand out on this point: first, the appropriation of social investment by the French subnational actors remains relative even if the notion’s influence is noticeable in their speeches; then, its spreading is hindered by governance’s complexity; finally, social investment is contributing to the development of a new vision of subnational territories in the management of social problems