The role of the welfare state has expanded beyond passive assistance and decommodificaton. In many countries, social investment policies now actively encourage (re)integration into the labour market. While the effectiveness of these policies is debated, we know even less about their broader social and political effects. In this contribution, we explore the impact of social investment policies on one key aspect of social life: political participation. Combining insights from social psychology with institutional analysis, we investigate the impact of three social investment policies (early childhood education, secondary education, active labour market policies) on two disadvantaged groups: young individuals from low-skill backgrounds; and single parents. Combining the European Social Survey with data on social investment, we find that these risk groups have reduced political efficacy and political participation. Social investment policies can alleviate these participation gaps in some cases, but not all.