In sexually monomorphic species, sex identification by molecular techniques is an important alternative. In this study, we employed molecular sexing to determine the sex of seven adult females, two immature females, one female with missing age data, and 21 adult males of White-throated Spadebills Platyrinchus mystaceus cancromus. The sex and age of each individual were associated with the presence or absence of a semi-concealed yellow coronal patch, typical of the species. All males displayed the semi-concealed patch, and four out of seven adult females also exhibited it. One of the two juvenile females exhibited a patch. The female with missing age data also exhibited the patch. This finding disputes previous reports that juveniles of this species do not have coronal patches. We conclude that semi-concealed yellow coronal patches are not sexually dimorphic in White-throated Spadebills. Both sexes can have a patch, but adults who do not have them are females.