The cap of Calonarius flavipavonius is brownish in color and purplish at the margins. It is convex, and sometimes becomes flat in age. It is slimy when wet and about 5-15 centimeters in diameter. The stipe is about 2.5-6.5 centimeters long and 1.1-2 centimeters wide at the top. It is whitish and can sometimes be yellowish or purplish at the top. A cortina is present. The gills are yellowish to light olive in color and are adnexed.