This article brings the analyses of the argumentative speech produced by a child. To do so, we retake the researches held in the Language Acquisition field (DEL RÉ et al., 2014a, 2014b), under the light of a dialogic and discursive approach (VOLÓCHINOV, 2017; BAKHTIN, 2013, 2016) and following the studies of Selma Leitão about Argumentation (1999, 2001, 2007a, 2007b, 2010; LEITÃO, BANKS-LEITE, 2006a; LEITÃO, FERREIRA, 2006a, 2006c; LEITÃO, VIEIRA, 2017, 2018). To carry out the discussions proposed, we will analyse the oral language production of a child (S. – 2; 1 to 3; 8 years), during interaction with the other(s), focusing on her argumentative productions. Such data was transcribed through the CLAN program, in accordance with the CHAT tool rules (MACWHINNEY, 2000), both enabling great detail of the productions. The results of our researches show that the children argument during situations of open polemic, when there is explicit opposition and when there is necessity (and possibility) of negotiation in and by the discourse. It is mobilized by the speaker since a young age, at two years and a month, in the case of S.