This is a long narrow flatworm, which is shiny black or dark brown on the upper surface, and mid-blue underneath (hence the specific epithet and the common name of "blue planarian".)

There is a narrow creamy/fawn or yellow coloured longitudinal stripe running down the center of the upper surface.

This flatworm is native to Eastern Australia, however it has been accidentally introduced to New Zealand,[1] the Balearic Islands,[2] Argentina,[3] Canary Islands,[4] France,[5] U.K (Portsmouth) and the USA (including California, Florida, Georgia, Texas, South Carolina and Iowa).

[6] It is found in moist forest areas, and during drier periods it shelters under rocks, rotting logs and in leaf litter.

[7] Its main characteristic is a cytochrome c oxidase subunit 2 gene of unusual length, with a cox2 encoded protein 505 aa in length (compared to about 250 aa in other geoplanids); this characteristic of a very long cox2 is also found in other members of the subfamily Rhynchodeminae, to which Caenoplana coerulea belongs.