Within the social movement literature, it is mostly assumed that the reasons why people join a protest demonstration are in line with the collective action frames of the organizations staging the protest. Some recent studies suggest, however, that protesters’ motives are only partly aligned with the messages that are broadcasted by social movements. This study argues that activists’ motives are for an important part shaped by mass media coverage on the protest issue. It investigates the link between people's reasons to protest, the campaign messages of the protest organizers, and newspaper coverage prior to the demonstration. Data cover 14 anti‐austerity demonstrations in Belgium, the Netherlands, and the United Kingdom. Results show that social movements depend a lot on other political actors to gain media visibility for their messages. Furthermore, the relationship between social movement frames and protest participant motives is mediated by newspaper coverage. Protest organizers’ are able to reach demonstrators via their own communication channels to some extent, but for many of their messages, they also rely on journalists’ reporting about the protest issue.