Memorial spaces can reinforce consensus or deepen conflict over the past. Memories of communism in Europe are particularly fraught mnemonic landscapes. Although they experienced the communist regime as a single country, Czechs and Slovaks now manifest very different political memories in public spaces with different levels of contention surrounding them. Through a media analysis (1993–2012) of events surrounding the 12 memorials addressing the communist past in the capital cities of Prague and Bratislava, this study generates a theory of differing levels of contention between societies with similar ‘difficult’ pasts. The Czech case is characterized by official and unofficial actors, who are cooperative or noncooperative, presenting often competing versions of the past through an individualistic, human rights-focused mnemonic frame. Slovak memory politics are less contentious, dominated by official memory actors, and interpreted through religion and nationalism. The collective memory literature lacks a way to understand when contention is more or less expected over a problematic past. I propose that when official memory actors privilege an individualistic mnemonic frame, contention becomes likely through the interpretations of unofficial memory actors, while a more collectivistic frame results in less contentious memory politics. In other words, the variation in mnemonic frame helps to explain why unofficial actors sometimes contest official representations of the past and other times leave them unchallenged.