This article analyses the process of adaptation of the Polish Ministry of Foreign Affairs (MFA) to EU membership and participation in CFSP, both before and after EU accession. It addresses changes in organizational structure, but also in institutional culture and everyday practices. Despite the initial ambiguity, Polish decision-makers tend to perceive CFSP as an opportunity rather than a constraint on national foreign policy. It is argued that the turning point of the Europeanization process took place in 2003, when Poland became an active observer to the EU and its diplomats were allowed to attend meetings inside the Council. The article also identifies and analyses the gaps in experience and knowledge between the diplomats posted to Brussels and those that stayed in Warsaw. Finally, it examines the various challenges that EU membership held for the MFA and how they have been dealt with so far.