[1] The Rio de Janeiro antwren is known only from the holotype and a few observations, and its taxonomy is unsettled.

[3][4][1][5] BirdLife International's Handbook of the Birds of the World (HBW) does not recognize it as a taxon but as a color morph of the silvery-flanked antwren (M.

[2][6] Gonzaga, who discovered the bird, noted that treating it as a color morph or a hybrid are plausible alternatives to full species status.

The holotype was collected at a site that had been studied for seven years, which prompted speculation by the original author and others that the bird could be a straggler or altitudinal migrant from the nearby Serra dos Órgãos.

[2] As of early 2024 neither xeno-canto nor the Cornell Lab of Ornithology's Macaulay Library have recordings of Rio de Janeiro antwren vocalizations.

Apparently some have been made, because authors note that the vocalizations are almost or entirely indistinguishable from those of the silvery-flanked antwren.