The Pacific reef heron was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae.

[2] Gmelin based his description on the "Sacred heron" that had been described in 1785 by the English ornithologist John Latham in his multi-volume work A General Synopsis of Birds.

[3][4] The Pacific reef heron is now placed with 12 other species in the genus Egretta that was introduced in 1817 by the German naturalist Johann Reinhold Forster.

[10] Pacific reef herons have yellow-grey legs, and the grey variety's throats and chins are marked by a narrow, white stripe.

They have brown beaks, gold-yellow coloured eyes and the surrounding areas of their faces are normally of a greenish to yellow cast.

[18] The species lay clutches of eggs year-round in colonies in the jungle, between palms and mangroves or in cavities of old buildings.

During the day, it hunts in shallow waters; standing motionless with wings open like an umbrella to reduce reflections and create shade which attracts fish.