Gouldian finches are sexually dimorphic, meaning that the males can be distinguished from the females visually. Typically, the male is the more vibrantly colored or more elaborately marked of the two sexes.

The hen is paler than the cock overall: the color of her back, breast,* and abdomen is less intense, and she has very little if any blue border around her mask. (*A lilac-breasted male may have a pale chest color like that seen in a normal hen, but in birds lacking this mutation, the purple color of the cock's breast is far more intense than that of the hen.) If the hen is yellow or red headed, she will likely have far more black feathering in her mask than the cock, who only has a thin black border around his mask. When in breeding condition, the hen's beak will become black (or red or yellow if she is yellow bodied). The cock generally has more vivid coloration on his back and abdomen, and has a larger blue border around his mask than the hen. When in breeding condition, the tip of his beak will become bright red or yellow. Although both cocks and hens can make simple shrill calling noises, ONLY cocks can sing.



Notice how the cock (left) has more vibrant and more extensive coloring than the paler, less well-marked hen (right).