Found in Eurasia, North America, New Zealand, and Australia, A. bernardii is a salt-tolerant species that grows in salt marshes, dunes, and coastal grassland.

The species was first described by French mycologist Lucien Quélet as Psalliota bernardi in 1879, based on collections made in La Rochelle, a seaport on the Bay of Biscay (France).

[5][6] An earlier (1999) analysis suggested that it is closely related to the "Agaricus clade", which contains A. subperonatus, A. devoniensis, A. bisporus, A. spissicaulis, A. bitorquis, and A. impudicus.

[7] In 1986, Henri Romagnesi placed it in section Chitonioides;[8] Solomon Wasser demoted this to a subsection of Duploannulatae in 1995,[9] and later provided molecular support for his decision.

In addition to A. bernardii, species in Wasser's concept of subsection Chitonioides include A. rollanii, A. bernardiiformis, A. gennadii, A. pequinii, and A. nevoi.

[1] Fruit bodies of A. bernardii have caps that range in shape from convex to flattened, and reach a diameter of 5–15 centimetres (2–6 inches).

A thick, white, rubbery partial veil covers the gills of the immature mushroom, and eventually remains as a ring on the middle of the stem.

[12] A. bitorquis, also edible, has a similar appearance, but can be distinguished by its double ring, and the lack of a fishy or briny odor.

[13] Once primarily a maritime species, the fungus has spread inland to roadside verges where salt has been applied to de-ice the roads.

The concentration of silver in the caps—which reached levels of up to 544 mg per kg of mushroom tissue (dry weight)—was about twice that of the stems.