In the south-western Pacific Ocean it is replaced by sibling species black-barred wrasse (Thalassoma nigrofasciatum).

[2] In its initial phase Jansen's wrasse is white with three black bars, the first of which is on upper half of head and anterior body and contains a yellow strip on the margin of the gill cover.

It is a carnivore and its diet includes benthic invertebrates and larger animals.

[1] Jansen's wrasse was first formally described as Julis jansenii in 1856 by the Dutch zoologist and military doctor Pieter Bleeker (1819-1878) with a type locality given as Manado on Sulawesi.

[5] The fish is named in honor of Albert Jacques Frédéric Jansen (d. 1861), an administrator in the Dutch East Indies who provided the type specimen.