This contribution proposes a framework of transnational parliamentarism to study inter-parliamentary cooperation, and applies it to the interparliamentary conference on CFSP/CSDP. It asks to what extent the IPC’s functioning reflects its constitutive intergovernmental logic, or whether its behaviour in practice might be guided by a transnational logic, hence becoming something more than just the parliamentary mirror of an intergovernmental cooperation framework. To this end we outline three functions that are brought forward by transnational parliamentarism: policy-making, collective accountability and cooperation, and investigate to which extent these logics can be observed in the functioning of the IPC CFSP/CSDP. Applying the framework reveals a nuanced picture of an inter-parliamentary cooperation framework which to some extent goes beyond purely intergovernmental functions of domestic accountability and representation, and also includes the performance of policy-making and parliamentary cooperation functions.