The fruit bodies (mushrooms) are small, with convex to flat, reddish to brownish caps up to 15 mm (0.6 in) in diameter, set atop thin cylindrical stems up to 4–7.5 cm (1.6–3.0 in) long with a rooting base.

A characteristic microscopic feature of the mushroom is the sharp, thin-walled cystidia found on the stipe, gills, and cap.

[1] In its taxonomic history, it has been moved to the genera Collybia by Paul Kummer in 1803, Marasmius by Jules Favre in 1939, and Pseudohiatula by Georges Métrod in 1952.

[7] The specific epithet tenacellus is a diminutive form of the Latin word tenax, meaning "tough".

The cylindrical stipe measures 4–7.5 cm (1.6–3.0 in) long by 0.5–2 mm thick, and has at its base a root-like pseudorrhiza that extends into the substrate.

Cheilocystidia (cystidia on the gill edge) are thin walled, plentiful, spindle-shaped to somewhat flask-shaped with a sharp tip, and measure 30–70 by 3–10 μm.

[19] Using a standard laboratory method to determine antimicrobial susceptibility, methanol-based extracts of Strobilurus tenacellus fruit bodies were shown in a 2000 study to have low antibacterial activity against the bacterium Bacillus subtilis, and low to moderate activity against the fungi Candida albicans and Aspergillus fumigatus.

In nature, the fungus secretes the chemical to prevent invasion by other fungi that challenge its nutrient source.

It works by blocking electron transfer in the mitochondria, stopping respiration by binding to the ubihydroquinone oxidation center of the bc1 complex.

[23] Because of their sensitivity to light, and high vapor pressures that causes them to rapidly disappear when applied to the surface of a leaf, chemically unmodified strobilurins are not generally useful as fungicides for agricultural use.