This article deals with the intellectual evolution and political activities of Carlos Keller Rueff between rhe early 1920s and the late 1930s. It discusses his development from a German nationalist to a Chilean fascist during the course of this eventful period. In the L920s Keller, who started his career in the Deutsch-Chilenischer Bund, the umbrella organisation of the German-Chilean community, expressed German National positions. Only at the end of the decade he began to distance himself from his narrow, sectarian German sub-culture and took a broader, national view, a development that coincided with his move from Concepción to Santiago and the failure of his plan to revive the immigration of Germans to Chile. With the book La eterna crisis chilena, published in 1931, he finally emerged as a Chilean nationalist and gained the reputation of an intellectual. One year later, in April 1932, he was, together with Jorge González von Marées, one of the founding members of the Chilean "Movimiento Nacional Socialista" (MNS). Keller became the movement's ideologue and its second most prominent leader. This career abruptly ended with the failed nacista coup of 5 September l938 and the subsequent transformation of the MNS into the "Vanguardia Popular Socialista".