[3] The fruit body of Thaxterogaster nebulobrunneus is sequestrate, meaning that its spores are not forcibly discharged from the basidia, and it remains enclosed throughout its development.

The colour of the outer skin of the cap (the pellis) is light orange-brown to brown; the surface is finely hairy and sticky.

Remnants of the white universal veil cover some of the cap surface and appear as a powdery coating; it is readily rubbed off with handling.

The internal spore-bearing tissue of the cap (the hymenophore) is bright cinnamon brown, and has irregular chambers that are 0.3–1 mm in diameter.

The basidia (spore-bearing cells) are hyaline (translucent), narrowly club-shaped, four-spored, and typically have dimensions of 25–28 by 5–8 μm.