[1][2] Echinaster sepositus has five relatively slender arms around a small central disc.

[3] It is a bright orange-red in colour, and has a soapy surface texture unlike superficially similar Henricia starfish (another somewhat similar species from the same region is Ophidiaster ophidianus).

The surface is dotted with evenly spaced pits from which the animal can extend its deep red gills (papula).

[4][5] Echinaster sepositus is found in the East Atlantic north of the Equator, including the Mediterranean Sea where it is one of the most common starfish (although virtually absent from some localities).

[5] It is found at depths of 1 to 250 m (3–820 ft) in a wide range of habitats, including rocky, sandy and muddy bottoms, and sea grass meadows (Posidonia oceanica and Zostera).