The Brilliant Emerald has apple green eyes and the abdomen and thorax are dark metallic emerald green with a bright bronze sheen. The wings are suffused by saffron, particularly in the female. In the male the abdomen is slightly club-shaped and is less hairy compared to that of the Downy Emerald . The abdomen of young specimens in particular will glint and flash in sunshine. There are also pale yellow markings laterally and ventrally on segments 2 and 3.

Larvae live amongst peat detritus, twigs, sticks and leaf litter, avoiding bare sand and gravel. Larvae are found under banks or stones; they like the dark and avoid the sunlight. They are commonest in parts that are heavily shaded by overhanging trees. They probably take at least two years to develop.