Diglossa humeralis is found from the subtropical zone to the páramo. This is an open alpine land that occurs from the treeline to the snowline and is most often wet and shrouded in a cloud of mist.
They are also commonly found in dense thickets that grow along the edges of wet to humid dwarf and elfin forest (citation).
Examples of prime Black Flowerpiercer habitat include: Polylepis ravines, eucalyptus plantations, shrubby clearings, hedgerows, parks and gardens (Restall et al. 2007).
Parker et al. (1996) list the primary habitat as semihumid/humid montane scrub. Additional habitats used by this species include the following, in decreasing order of importance: the second-growth scrub, the eflin forest, and the edges of the mountain evergreen forests.