Current bird lists treat the Diademed Tanager as Stephanophorus diadematus; historical sources also used S. leucocephalus. It is dark blue-violet with a white-blue and red crown. A study of 33 adult skins found brighter male crowns, and one male was recorded feeding in Paraguay.
The study describes the overall colour as dark blue-violet with a white-blue and red crown. Reflectance measurements of 33 adult study skins found brighter male crowns and sex-related differences in the nape, chest, and belly. The sampled nonbreeding birds were brighter than breeding birds.
A Paraguayan annual-cycle study observed one male eating Eugenia uniflora fruit in an isolated tree about 3 m tall near the hotel. This is a single field observation.
An extinction-risk assessment has not been added yet.