Shells of Mitra papalis can reach a length of about 60–166 millimetres (2.4–6.5 in).[2] The form of these large shells is similar to a Papal mitre (hence the common name). They are elongate to ovate, fusiform and smooth but without axial streaks on the surface. Sutural coronations are present. The aperture is moderately wide, smooth within. The shell surface is white, with small white nodules under sutures and with several rows of irregular bright red-orange or purplish blotches.[4]
This species is quite similar to Mitra stictica, but its body form is longer, with more adpressed sutures and wider nodules.[4]