‘The fatal fact of the woman writer’ is a phrase coined by the Argentine author Alberto Pineta in the late 1920s, a time marked by women’s growing presence in the cultural sphere. On both sides of the Atlantic, women expressed an acute interest in the avant-garde literary culture and faced similar challenges in their attempt to negotiate their place in the literary field. By considering Spanish-speaking women as mediators across cultural and geographical borders, this study seeks to move beyond the concepts of ‘centre’ and ‘periphery’ in order to rethink the avant-garde as a transnational and multifaceted phenomenon. To explore the intertwined trajectories of Gabriela Mistral, Alfonsina Storni and Ernestina de Champourcín, this study examines their literary activities in Madrid and provides a comparative analysis of the avant-garde themes that recur in their poetry. Special focus is set on the transnational processes that shaped their work and allowed them to assert their identity as female writers and poets.