It grows to a carapace width of 90 mm (3+1⁄2 in), and feeds on a variety of mollusks, worms, and small crustaceans, affecting a number of fisheries.

Its successful dispersal has occurred by a variety of mechanisms, such as on ships' hulls, sea planes, packing materials, and bivalves moved for aquaculture.

The undulations, which protrude beyond the eyes, are the simplest means of distinguishing C. maenas from the closely related C. aestuarii, which can also be an invasive species.

Another characteristic for distinguishing the two species is the form of the first and second pleopods (collectively the gonopods), which are straight and parallel in C. aestuarii, but curve outwards in C. maenas.

Appearances of C. maenas have been recorded in Brazil, Panama, Hawaii, Madagascar, the Red Sea, Pakistan, Sri Lanka, and Myanmar; however, these have not resulted in invasions, but remain isolated findings.

[18] Based on the ecological conditions, C. maenas could eventually extend its range to colonise the Pacific Coast of North America from Baja California to Alaska.

This led the Lummi Indian Business Council to declare a disaster in November 2021 and the Washington Department of Fish & Wildlife to request emergency funding from the Governor.

[23] C. maenas can live in all types of protected and semiprotected marine and estuarine habitats, including those with mud, sand, or rock substrates, submerged aquatic vegetation, and emergent marsh, although soft bottoms are preferred.

A molecular biological study using the COI gene found genetic differentiation between the North Sea and the Bay of Biscay, and even more strongly between the populations in Iceland and the Faroe Islands and those elsewhere.

[25] Females can produce up to 185,000 eggs, and larvae develop offshore in several stages before their final moult to juvenile crabs in the intertidal zone.

[27] C. maenas has the ability to disperse by a variety of mechanisms,[26] including ballast water, ships' hulls, packing materials (seaweeds) used to ship live marine organisms, bivalves moved for aquaculture, rafting, migration of crab larvae on ocean currents, and the movement of submerged aquatic vegetation for coastal zone management initiatives.

[26] The prey of C. maenas includes the young of bivalves[34] and fish, although the effect of its predation on winter flounder, Pseudopleuronectes americanus is minimal.

[35] C. maenas can, however, have substantial negative impacts on local commercial and recreational fisheries,[28] by preying on the young of species, such as oysters (adults' shells are too tough for C. maenas to crack)[28] and the Dungeness crab,[28] or competing with them for resources[36] and eating the Zostera marina that Dungeness and juvenile salmon depend upon for habitat.

[37] Due to its potentially harmful effects on ecosystems, various efforts have been made to control introduced populations of C. maenas around the world.

[40] Host specificity testing has recently been conducted on Sacculina carcini, a parasitic barnacle, as a potential biological control agent of C. maenas.

[44] Several groups in New England have successfully adapted these methods to produce soft-shell green crabs from the invasive species.

[46] One of the book's co-authors went on to found Greencrab.org, an organization dedicated to developing culinary markets for the invasive green crab.

[48] Specifically, one study evaluated the consumer acceptability of empanadas (fried, stuffed pastries) which contained varying amounts of green crab mince meat.

[52] C. maenas is fished on a small scale in the northeast Atlantic Ocean, with about 1200 tonnes being caught annually, mostly in France and the United Kingdom.

[54] An earlier description was published by Georg Eberhard Rumphius in his 1705 work De Amboinsche Rariteitkamer, calling the species Cancer marinus sulcatus, but this antedates the starting point for zoological nomenclature.