Parliamentary diplomacy (PD) is a contemporary feature of modern parliamentarism but remains, thus far, underexplored from a gender lens. PD incorporates the relationships that parliamentarians or parliaments as institutions have with other parliaments, parliamentarians, and nonstate actors to foster peace, democracy, understanding, dialogue, legitimacy, and scrutiny of governments. Parliaments are spaces of parliamentary and international negotiation and communication, practiced through rules, practices, and symbols. This article draws on a single case study of the European Parliament (EP) and of Members of the European Parliament (MEPs) gendered PD, at the time of Brexit—a period when international agreements and relationships were shaped and how gendered PD was culturally legitimized. It is based on a unique qualitative dataset of 140 interviews and ethnographic research (2018–2020) generated at the time of the withdrawal of the United Kingdom’s MEPs from the EP. Based on this analysis, it further considers what a feminist PD might look like.