This article aims to show how the conversion to a vegetarian diet represents highly relevant empirical material for the sociology of collective mobilization and activism. It draws on 39 interviews with animal rights activists who refuse to eat meat or other products derived from the exploitation of animals. This empirical material is used to specify the categories of analysis required to take into account the affective dimensions of activist commitments. This perspective attempts to best describe the multiple and complementary dimensions of activists’ work and careers.