The adult white-throated spadebill is 3.8 in (9.7 cm) long, weighs 0.33 oz (9.3 g), and has large eyes and a very short tail.
Sexes are similar, other than the female having a smaller crown patch, but young birds are brighter and ruddier above, lack the crown patch, and have a grey throat and breast shading to a whitish belly.