[1][3] It is the largest known species of Neotropical freshwater prawn, growing up to 30 centimetres (12 in) long and weighing as much as 850 grams (30 oz),[4] although even larger specimens have been reported.

[5] It is an important species for commercial fishing in the Sao Francisco River basin, where it is known by the local name of pitu.

[6] M. carcinus is omnivorous, with a diet consisting of molluscs, small fish, algae, leaf litter and insects.

[7] Macrobrachium carcinus has a tan or yellow body with dark brown stripes.

Its chelae are unusually long and thin, to facilitate foraging for food in small crevices,[7] and may be blue or green in color.