The banded sea urchin has a slightly oval test (shell), reaching a diameter of about 5 cm.

[1] The anal papilla is big, more or less translucent and very obvious on the aborale face; it is generally whitish and speckled with black and white dots, circled by a ring of visual receptors that grant it rudimentary vision.

In its darkest forms, it can be confused with its cousins Diadema setosum or Diadema savignyi (which can both keep banded radiola when adult) ; however, the latter is bigger, more uniformly black, has less discernible secondary radioles and is recognizable in five characteristic white points at the top of its test as well as in orange-colored circle around its anus.

The most common confusion is with the very close species Echinothrix diadema, which can have banded spines when young.

[1][3] It occurs from the surface to 70 metres (230 ft) depth and can be found in lagoons, external reef slopes and channels.