Are avant-garde elements added to historical objects as a temporary fashion to fulfill the aspirations of designers or an attempt to draw attention to themselves? It may be the exact opposite, and this type of controversial project is the best lifebelt for such monuments. This article explores issues related to external avant-garde elements added to adapted churches and their influence on the efficiency of such adaptation projects. Gothic churches located in the north of Europe that have changed their religious function, entirely or in part, were considered. This work examined former churches in Maastricht, namely, the Minorite Church, the Church of the Kruisheren Monastery, the Dominican Church, as well as Polish churches located in Gdańsk, including St. John’s Church and St. Catherine’s Church. This article attempted to identify the factors that contribute to the successful adaptation of former churches and the benefits and drawbacks of adopting avant-garde design solutions. Results of this study might provide valuable inspiration for other churches that are losing worshippers. This study was conducted on the basis of a wide range of literature, statistical data, logical reasoning, and comparative methods. Observations from selected edifices were checked for their correlation over time. This study also included in situ investigations.