Abstract The article argues that contact between the German, Austrian, and Italian radical nationalist milieux through the long 1920s represented a specific form of fascist relationship-building which should be understood in terms of fascist transnationalism: a cross-border networking process that took place against the backdrop of fluid, evolving social relationships. Starting from the analysis of the mutual exclusiveness of radical nationalist mobilizations, the article highlights the analytical limits of the concept ‘internationalism’ when applied to early fascist relationships that developed in transnational, informal settings. Then, it makes an argument for a processual approach based on the observation of relational practices, while sketching out the peculiarities of these milieux. Accordingly, it outlines the development of the trilateral networking process between German, Austrian, and Italian organizations (Stahlhelm, DNVP, NSDAP, Heimwehren, and PNF) along its different stages. Finally, it offers an outlook on the key features of fascist transnationalism grounded in the historical analysis of this specific triangular case study.