This paper presents a study on collaborations between museum professionals and municipal organizations in their dealings for safeguarding heritage. Since 2001, Danish cultural-historical museums have been legally required to promote the preservation of significant heritage assets in historical buildings and environments of recent modern history. Taking three provincial municipalities and their local museums as the empirical starting point, this interview study was aimed at shedding light on a specific branch of museum collaborations where the enactment of heritage in relation to public planning administration is at stake. Several challenges confronting museum professionals in this field were identified. However, analytically investigating co-existence also revealed that effective ways of overcoming the aforementioned challenges are constituted occasionally during the collaborations. Finally, it is suggested that a self-reflective continuation of engagement in practical projects might be just as effective for improving museum–municipal collaborations as an adjustment of legal regulations in this area.