This article analyses the presence of ethnography, especially the German ethnographic tradition, in part of the oeuvre by the historian Sergio Buarque de Holanda. In order to achieve this, we will focus on the book Caminhos e fronteiras (1957), a collection of essays written during the decade in which Sergio Buarque was the director of the Museu Paulista (1946-1956). This article is divided in two interconnected parts, namely, one about the authors experience when directing the Museu Paulista and how he got in contact with ethnology in that period; and one on how themes and concepts that were important in the German ethnological tradition also play a significant role in the book Caminhos e fronteiras. We intend to prove that ethnography was a central part of Sergio Buarques analysis of the colonization of the outskirts of Portuguese America.