This species is a simple, solitary ascidian, with a tough outer covering or tunic. The body is globular to ovoid in shape, measures 1-2 cm in diameter, and attaches to the substrate at its base. The oral and atrial siphons are positioned anteriorly, well separated, and characterized by tentacle-like processes around the openings (oral siphon 6-lobed; atrial siphon 4-lobed). Overall, the tunic is translucent to greyish-green in color; the surface is sparsely covered with very short hairs that typically remain free of sand grains or debris.
In the Northeast Pacific, Molgula manhattensis is most similar to other molgulid tunicates, including M. retortiformis Verrill, 1871 and another non-native species found in the region, M. manhattensis (De Kay, 1843).
Molgula citrina has been found recently in south-central Alaska (Lambert et al. 2010). It remains unclear whether this record represents a new invasion or a previously overlooked circumpolar distribution. The species is native to the North Atlantic, with a wide geographical distribution ranging from northeast North America to Great Britain and northern Europe.