Social and political trust are crucial for societal well-being and are linked to lower levels of corruption as well as to the size of the welfare state. Interpersonal trust is shaped through attachment-related experiences in close interpersonal relationships. However, previous research has not linked these two strands of research, yielding an important knowledge gap about the potential implications of attachment for social and political trust. Therefore, we investigated whether attachment orientations are related to both social trust and trust in the welfare state. Data were collected in two countries with different organization and size of the welfare state, the United States (n = 284) and Sweden (n = 280). In both countries, attachment-related avoidance (but not anxiety) was negatively related both to social trust and trust in the welfare state, even after controlling for pertinent confounds. Our findings also suggested that social trust may mediate the link between avoidance and trust in the welfare state. These results cohere with an assumption that people’s attachment-related working models may extend to their models of the world at large. We conclude that interpersonal parameters should be considered to fully understand the development of trust in political institutions.