The poorly known and apparently generally uncommon Todd’s Antwren occurs syntopically with another congener, the Spot-tailed Antwren (Herpsilochmus sticturus), and these two species are only easily separated by their loudsongs and, with good views, by their female plumages. Both these species may be found accompanying mixed-species foraging flocks of insectivores in the canopy of tall evergreen forest, but the Todd’s Antwren is just as frequently encountered alone, in pairs, or in small family groups. It is only rarely observed in seasonally flooded areas, or in savanna woodlands. This species’ general behavior and ecology are poorly known, and nothing has been published to date concerning its breeding biology. The Todd’s Antwren appears to form a superspecies with the recently described Ancient Antwren (Herpsilochmus gentryi) of northeast Peru and southeast Ecuador, and both species show some vocal similarities with the three species in the Bahia Antwren (Herpsilochmus pileatus) complex.