This worm is found in the eastern Atlantic Ocean, the Mediterranean Sea and in various locations in the Indo-Pacific region at depths down to about 1,000 m (3,300 ft).

The oral disc is at the tip of the introvert; this has a terminal mouth and a cluster of ten to twelve short tentacles arranged in a crescent surrounding a nuchal organ.

[2] Aspidosiphon muelleri occurs in the Mediterranean Sea and the eastern Atlantic Ocean, its range extending from the Shetland Islands to West Africa.

It often occupies empty gastropod or tusk shells, or resides in serpulid tubes, holes or crevices, or among the branches of coralline algae or the deepwater coral Lophelia pertusa.

[2] In Australia it is reported as being an obligate commensal inside solitary, free-living corals such as Heterocyathus aequicostatus and Heteropsammia cochlea.