The pink-eared duck was first described by the English ornithologist John Latham in 1801 under the binomial name "Anas membranacea". It is the only living member of the genus "Malacorhynchus"; a closely related, but slightly larger extinct form from New Zealand was described as Scarlett's duck ("Malacorhynchus scarletti"). This peculiar duck may be most closely related to the shelducks but its relationships are enigmatic. It may be closer to the musk duck and the stiff-tails (Sraml "et al." 1996) and, formerly placed in the paraphyletic "perching ducks"; it is in any case not close to the dabbling ducks.