Is it true that national identity increases trust, as liberal nationalists assume? Recent research has studied this side of the ‘national identity argument’ by focusing on conceptions of the content of national identity (often civic or ethnic) and their links to social, rather than political, trust. This paper argues that if we take social identity theory seriously, however, we need to complement this picture by asking how varying the strength – rather than the content – of a person’s sense of their national identity affects both their social and political trust. We break down the different dimensions of national identity, hypothesizing and empirically verifying that there are divergent links from national attachment, national pride, and national chauvinism to social and political trust. We do so with data from the US (General Social Survey) and the Netherlands (Longitudinal Internet Studies for the Social Sciences ), thus expanding current knowledge of national identity and trust to a highly relevant yet neglected European case.