[3] The brown-breasted bamboo tyrant has two subspecies, the nominate H. o. obsoletus (Miranda-Ribeiro, 1905) and H. o. zimmeri (Traylor, 1979).

The nominate subspecies is found in western Rio de Janeiro and eastern São Paulo states in southeastern Brazil.

It typically forages singly or in pairs and is not known to join mixed-species feeding flocks.

It feeds mostly in undergrowth between about 1 and 3 m (3 and 10 ft) of the ground, using short upward strikes to the underside of leaves from a perch.

[4] The brown-breasted bamboo tyrant's breeding season has not been detailed but includes November and December in southeastern Brazil.

One well described nest was a globe with a domed roof and a side entrance that had a small "visor".

What may be either the song or a call of the brown-breasted bamboo tyrant is an "irregular series of very high 'tic' notes".

"Montane forests have suffered less destruction than have adjacent lowland areas, but isolated patches in [north] of this species’ range have virtually disappeared owing to expansion of pasture and cultivation.