Political parties throughout Europe are witnessing a significant professionalization of their daily functioning. Professionalization refers to an institutional process “by which professionals become more central to an organization, in this case a party†(Webb & Kolodny 2006: 338). The centrality of professionals is most obvious in parties’ reliance on an expanding body of professional staff members and experts with specialized skills (a.o. marketing professionals, consultants, spin-doctors and public relations experts) performing traditional party functions and supporting the leadership in the management of the party. These professionals replace – or at least complement – member-volunteers and party bureaucrats in the party apparatus (Norris 2000). Although party professionalization is a phenomenon that has received considerable academic attention, research on the professionalization of Belgian political parties remains scarce. In this paper, we will study –in an explorative way– to what extent and how professionalization has taken/is taking place in the Belgian parties, focusing on gender equality. On the one hand, we will ‘map’ the presence of “gender professionals†in Belgian parties: who are they, what are their main tasks, to what extent is their presence institutionalized in the party and how has this changed over time? On the other hand, we will reflect on the consequences of the presence of “gender professionals†for the internal dynamics and power relations within parties. We conduct an in-depth case study of one particular policy domain, but we will reflect on the broader implications for processes of party professionalization in other domains as well. We explore the professionalization of gender equality in 11 Belgian parties based on new and original data (including document analysis and interviews) gathered by the authors in 2006 and 2014. The results show that party professionalization is overall limited. Although parties have included gender experts in their organization ...