The international #MeToo campaign against sexual harassment constitutes the most prominent contemporary campaign against sexual harassment worldwide. It exposed the issue by undermining the ‘culture of silence’ prevailing in several contexts, including political institutions. This article analyses one specific variant of #MeToo, the campaign MeTooEP that emerged in the European Parliament (EP). MeTooEP is unique in many ways: it was the first collective action against sexual harassment in parliaments emerging in the #MeToo aftermath and it was the first collective action within the EP led by members of the staff, which eventually drove some internal policy changes. Using a unique, large interview dataset, the analysis shows how the actors behind MeTooEP were crucial in shaping the campaign. Their knowledge of institutional rules, practices and daily presence in the EP facilitated their advocacy and transformed the Parliament into an enabling platform for their actions. With the help of Feminist Institutionalism, the analysis demonstrates how the formal and informal institutional EP bodies with their rules and regulations shaped MeTooEP in ways that constrained and empowered it.