The puzzle to be explained in this article is how and why parties experience variation in the degree of moderation in nationalism. The article submits that an important indicator for such variation can be found in the extent to which a party is transnationally embedded, but the central claim of this article is that while external influences may well temper party nationalism they are filtered through predominantly internal factors, notably the cleavage structure and the political culture. The explanatory power of this argument is tested through a comparative case study of relative moderation in nationalism of two Baltic post-communist national conservative parties, Pro Patria Union in Estonia and For Fatherland and Freedom/LNNK in Latvia, with particular attention to party preferences and positions on national questions, as well as of engagement in transnational party cooperation. Both started out as national conservative parties, but whereas the former party has turned into a more mainstream conservative party of European stance and a moderate nationalist party the latter has remained radical nationalist and basically held on to (ethno-) nationalism. The article examines the sources of this variation.