Historical perpetrator groups are often implicated in multiple transgressions, yet psychological research on collective memory has predominantly focused on isolated instances of wrongdoing. The present research advances this literature by examining how members of perpetrator groups negotiate different memories of ingroup transgressions. Using Germany as the empirical context, we employed a sequential mixed-methods design across five studies. A qualitative analysis of online discussions (Study 1, N = 458 comments) provided the basis for developing a scale that distinguishes inclusive from exclusive approaches to collective remembering of ingroup perpetration. Inclusive approaches acknowledge the importance of remembering multiple instances of ingroup perpetration, whereas exclusive approaches prioritize one instance of ingroup transgressions. Subsequent quantitative studies evaluated the psychometric properties of the developed scale (Studies 2a, 2b) and investigated the nomological network of the two approaches, exploring their links to historical defensiveness, social identity, and sociopolitical attitudes (Studies 2a, 2c, 3, total N = 1491).