Karsten included three species: P. cyathiformis, P. melaleucus, and the type, P. niger (originally published with the epithet "nigrum").

[2] Fruitbodies of Phellodon niger have a cap and a stipe, and so fall into the general class of "stipitate hydnoid fungi".

Caps are flat to depressed to somewhat funnel-shaped, with a felt-like texture at first before developing concentric pits, wrinkles, and ridges.

In conditions of high humidity, P. niger can form striking drops of black liquid on the actively growing caps.

Phellodon niger has a monomitic hyphal system, producing generative hyphae with a diameter of 2.5–5 μm.

[15] Phellodon niger was included in a Scottish study to develop species-specific PCR primers that can be used to detect the mycelia of stipitate hydnoids in soil.

[16] Collections labelled as P. niger from the United Kingdom that were DNA tested, revealed additional cryptic species.

[19] Phellodon niger has been a source for several bioactive compounds: the cyathane-type diterpenoids, nigernin A and B; a terphenyl derivative called phellodonin (2',3'-diacetoxy-3,4,5',6',4''-pentahydroxy-p-terphenyl); grifolin; and 4-O-methylgrifolic acid.