The heritage of World War II left an indelible mark on the relations between Italy and Yugoslavia. During the détente period, however, these two countries were able to overcome many historical resentments and established a fruitful co-operation in Cold War Europe. This article questions the engagement on state, regional and municipal levels and analyses the role of twin cities in this multilayered process. With the help of primary sources, we learn how the heritage of World War II played an important role in building new forms of post-war co-operation. In fact, post-war twinning is often the result of shared anti-fascist activities from the war years. However, this is not confined to communist municipalities or ‘red’ regions in Italy on one side, and socialist Yugoslavia on the other, but is a more fluid and flexible practice which involves historical ties, geographical positions, personal capacities and economic needs.