Both sexes of all subspecies have a white spot behind the eye and a forked tail, though that of the female is not as deeply indented as the male's.

[6] Adult males of the nominate subspecies have a glittering green to blue-green head and breast with a small metallic violet-blue patch on the throat.

Immature males have a dull bronzy green crown and underparts, a bright buff chin and malar, and a shallowly forked tail.

Males of H. j. jamersoni are much duller than the nominate on the head and breast; their tail is shorter and its central feathers have a green gloss.

[6] The nominate subspecies of green-crowned brilliant is found from Panamá Province in eastern Panama into Colombia, where it inhabits all three Andean ranges.

H. j. henryi is found more northerly, from Costa Rica south and east into Panama as far as Coclé Province.

[6] The green-crowned brilliant's nesting season in Costa Rica is thought to span from July or August to January and in Colombia from May to September.

The nest is a bulky cup of plant fibers and scales of tree ferns saddled on a thin down-sloping branch, typically between 2 and 6 m (7 and 20 ft) above the ground.

It "shows some tolerance of habitat fragmentation, degradation and disturbance [but] outright forest clearance is expected to cause local population declines".