--- - |2 Abstract Adding to the literature on non‐institutional political action and trust, this article argues that the loss of institutional trust is not only a cause but also an outcome of political activism. Studying the Danish refugee solidarity movement in a mixed‐methods research design including survey and qualitative interview data, the article shows that three kinds of activism – political activism, humanitarian activity, and civil disobedience – relate differently to the loss of trust in the institutions of the Parliament, the legal system, and the police. Political activism primarily affects a loss of trust in the Parliament due to low external efficacy and a closed political opportunity structure. Civil disobedience affects a loss of trust in the legal system and the police due to a perceived lack of procedural justice. Humanitarian activity does not affect a loss of institutional trust because it does not imply interaction with the institutions to the same extent as the other kinds of activism. The consequence of losing trust in the political institutions is not an abandonment of democratic values, nor political apathy, but rather a change in civic engagement from a mode of democratically legitimizing participation in the institutions to a mode of contending and questioning the legitimacy of the political institutions. This finding indicates that in turn loss of institutional trust may cause an increase in extra‐institutional political action which is consistent with the commonly assumed causality in the literature. This leads to a final integrating argument for conceptualizing activism and loss of institutional trust as reinforcing factors in a process where, in line with the main finding of this study, activism may cause a loss of institutional trust which, in turn, may cause additional activism, as argued in the existing literature. - 'The British Journal of Sociology, Volume 70, Issue 4, Page 1198-1224, September 2019. '