This article studies the co‐operation between parliamentary and executive diplomats in EU foreign policy. Building on transnational perspectives, the European Parliament is conceptualized as an actor capable of pursuing autonomous diplomatic behaviour through cross‐border agency over its elected representatives, its bureaucracy, as well as through European party federations. A novel framework is proposed, built around the hypothesis that parliamentary and executive actors co‐operate by exchanging institutional, information, legitimacy and access resources in order to reach their goals more effectively. To demonstrate the argument empirically, the article studies EU‐facilitated mediation talks in Macedonia (2015–17). Building on semi‐structured interviews with 27 key stakeholders, the analysis shows how during the different stages of the mediation, executive and parliamentary actors exchanged crucial diplomatic resources in order to effectively conclude and implement the so‐called Pržino‐agreements between the government and opposition parties.