The sexes of the red wattlebird are similar in size and plumage, the length of the adult male ranging from 33 to 37 centimetres (13 to 15 in) and the adult female from 34 to 37 centimetres (13 to 15 in).
With an average weight of 100–120 grams (3.5–4.2 oz), the red wattlebird is one of the largest nectar-feeding birds in the world, and the second largest species of honeyeater native to Australia, eclipsed only by the yellow wattlebird.
The crown, forehead and upper lores (area between the eyes and nostrils) are dark brown, streaked with pale brown at the front of the crown and white at the rear of the crown.
The nape (back of the neck) is slightly paler brown, with white streaks.
A whitish triangular marking covers the lower lores and anterior ear covert feathers, bordered below by a dark brown stripe from the lower mandible down to the wattle and around to behind the eye.
The throat is dark brown streaked with white.
The iris of the eye is orange-red to crimson.
The distinctive pinkish-red wattles dangle from the lower rear corner of the ear coverts on either side of the neck, and there is a sliver of pink bare skin at the lower border of the white patch on the face.
The chest and belly are streaked white, and there is a bright yellow patch towards the tail.
The strong legs and feet are pink or pinkish-brown, and the downward-curving bill is black.
The average dimensions of the bill are 23.5 millimetres (0.93 in) long, 6.7 millimetres (0.26 in) wide, and 6.8 millimetres (0.27 in) high at its base.
The gape is grey-black, while the inside of the mouth is orange.
In common with other honeyeaters, the red wattlebird has a long, specialized tongue to extract nectar from flowers.
The tongue can extend well beyond the tip of the bill, and is divided at the end to form a brush-like structure with over a hundred bristles that soak up nectar by capillary action.

The red wattlebird begins moulting after the breeding season, starting with the primary flight feathers in November or December, and finishing between the following March and May. The feathers of the breast, back, median and lesser covert feathers are moulted before those of the crown, remiges, and rectrices.

Immature red wattlebirds are generally less flamboyant.
Juveniles have much less prominent wattles, brown irises, a pale crown, and much less yellow on the belly.
They moult into first immature plumage within a few months of leaving the nest.
First immature birds are more similar to adults overall, having red irises with brown rings, wattles larger but still smaller than adults, and a greyish pink gape.

The red wattlebird is hard to confuse with any other species, though in poor visibility it might be mistaken for the spiny-cheeked honeyeater, or little or western wattlebirds.
The sexes of the red wattlebird are similar in size and plumage, the length of the adult male ranging from 33 to 37 centimetres (13 to 15 in) and the adult female from 34 to 37 centimetres (13 to 15 in). With an average weight of 100–120 grams (3.5–4.2 oz), the red wattlebird is one of the largest nectar-feeding birds in the world, and the second largest species of honeyeater native to Australia, eclipsed only by the yellow wattlebird. The crown, forehead and upper lores (area between the eyes and nostrils) are dark brown, streaked with pale brown at the front of the crown and white at the rear of the crown. The nape (back of the neck) is slightly paler brown, with white streaks. A whitish triangular marking covers the lower lores and anterior ear covert feathers, bordered below by a dark brown stripe from the lower mandible down to the wattle and around to behind the eye. The throat is dark brown streaked with white. The iris of the eye is orange-red to crimson. The distinctive pinkish-red wattles dangle from the lower rear corner of the ear coverts on either side of the neck, and there is a sliver of pink bare skin at the lower border of the white patch on the face. The chest and belly are streaked white, and there is a bright yellow patch towards the tail. The strong legs and feet are pink or pinkish-brown, and the downward-curving bill is black. The average dimensions of the bill are 23.5 millimetres (0.93 in) long, 6.7 millimetres (0.26 in) wide, and 6.8 millimetres (0.27 in) high at its base. The gape is grey-black, while the inside of the mouth is orange. In common with other honeyeaters, the red wattlebird has a long, specialized tongue to extract nectar from flowers. The tongue can extend well beyond the tip of the bill, and is divided at the end to form a brush-like structure with over a hundred bristles that soak up nectar by capillary action.
The red wattlebird begins moulting after the breeding season, starting with the primary flight feathers in November or December, and finishing between the following March and May. The feathers of the breast, back, median and lesser covert feathers are moulted before those of the crown, remiges, and rectrices.
Immature red wattlebirds are generally less flamboyant. Juveniles have much less prominent wattles, brown irises, a pale crown, and much less yellow on the belly. They moult into first immature plumage within a few months of leaving the nest. First immature birds are more similar to adults overall, having red irises with brown rings, wattles larger but still smaller than adults, and a greyish pink gape.
The red wattlebird is hard to confuse with any other species, though in poor visibility it might be mistaken for the spiny-cheeked honeyeater, or little or western wattlebirds.
Red wattlebird