Its breeding habitat is forest canopy and edges at altitudes up to 1675m, and this bird can also be found in tall second growth and shady gardens . The female lays two white eggs in a small conical cup nest, which is made of plant down and sited near the tip of a thin branch.
The purple-crowned fairy is 11.5 cm long and weighs 6.5 g. It is slender and has bright white underparts, a green back, and a long pointed tail which has black central and white outer feathers. There is a dark patch through the eye, and the bill is sharply pointed. The male has a purple crown and a purple spot at the end of the eyepatch, which is bordered below with a glittering green malar stripe. The song is a vigorous repetition of the high thin tsit call.
The female lacks the purple and glittering green colours on the head, and the immature bird has rufous fringes to its upperpart plumage and a dusky throat.
The purple-crowned fairy has a very light and graceful flight. It eats insects, picked off the foliage or caught in flight, and takes nectar from flowers, piercing the bases of larger blooms such as Heliconia. Although not particularly territorial, this species is quite aggressive, and will resist the attacks of territorial species.