The Serra do Mar tyrannulet (Phylloscartes difficilis) is a small species of bird in the family Tyrannidae. It is endemic to humid montane forest in the Serra do Mar in south-eastern Brazil. More likely confused with the short-tailed and pale-eyed hangnest tody-tyrant than other members of the genus Phylloscartes, its bright olive-green upperparts contrast strongly with the grey underparts. It is generally uncommon and threatened by habitat loss.