Mico argentatus occurs south of the Rio Amazonas, in relatively flat, lowland forest, between the mouth of the Rio Tocantins in the east and the Rios Tapajós and Cuparí (an eastern tributary) in the west (Ferrari and Lopes Ferrari 1990; Ferrari and Lopes 1996; Vaz 2001; Pimenta and Silva Jr. 2005), extending south to the Rio Irirí as far as the lower Rio Curuá (Hershkovitz 1977). Ferrari and Lopes Ferrari (1990) (see also Ferrari 1993; Ferrari and Lopes 1996) argued that its restricted range (lowland floodplain) east of the Rio Tocantins is due to habitat differences and sympatry with the Black-handed Saguinus niger (a wider ranging species extending between the Rio Xingu and east to the Rio Parnaíba).

Mico argentatus does not occur south of Belo Monte on the Rio Xingu (Transamazon highway) and is restricted to the north of the Tucuruí dam reservoir on the Rio Tocantins (Ferrari and Lopes Ferrari 1990; Ferrari and Lopes 1996). This restricts the range of M. argentatus well to the north of the mouth of the Rio Irirí on the eastern bank of the Xingú, with the southern limits being somewhere between the Rios Cuparí and Irirí to the west of the Rio Xingu as indicated by Hershkovitz (1977; see also Martins et al. 1988).

Ferrari (2008) pointed out that there is probably a zone of contact between M. argentatus and M. leucippe in the south-west of the formers range, but there is a gap in our knowledge of the occurrence of this genus between the Rios Teles Pires and Irirí.