This article argues that transnational engagement offers political parties legitimacy and reinforces tendencies towards standardization. EU accession brought many parties in post-communist Europe into Euro-parties and political groups. In this context, national parties are expected to adhere and keep to certain standards. The case in point is the Estonian Social Democratic Party, which took back this name shortly before Estonia joined the EU. The article shows how this party has been seeking to develop into a modern European social democratic party by engagement in a range of transnational networks and activities and by embracing the organizational and programmatic ideals of its partner parties