Based on very limited evidence, Viegas Barros (1992) suggests that Puelche might be closely related to the language of the Querandí, one of the Het peoples, and Viegas Barros (2005) that it is related to the Chon languages.

In 1829, D'Orbigny toured the area of southern Buenos Aires and the mouth of the Río Negro.

There he collected words of the “puelches”, “aucas” and “tehuelches” —that is, in günün a iajüch, mapuzungun and teushen, respectively—in the vicinity of Carmen de Patagones, in a permanent settlement of linguistically heterogeneous groups.

The French traveler, intrigued by the indigenous languages of the area, arrived at the tolderías and contacted some interpreters: "In a tent of friendly Patagonians I found a woman named Lunareja who spoke enough Spanish as if to serve as an interpreter; belonged to the Puelche nation and was married to a Patagonian, so that I knew both languages equally, which was of the greatest use to me.

"In L'Homme américain (de l'Amérique méridionale) he includes some comments on which highlights pronunciation features, the use of the morpheme ya- prefixed to the parts of the body, the numbering system or the absence of gender markings on adjectives, as well as a list of words that compares with those of other languages of South America.