Whereas grasshoppers have short, forward-pointing antennae, bush-crickets have long, filamentous antennae which they frequently flick from back to front. Like several other species of bush-cricket, the dark bush-cricket has a humped back.
The dark bush-cricket is usually heard before it is seen. Its song is a high chirrup which is often given in quick succession by several individuals in the same clump of brambles. As its name implies, its main colour is dark grey-brown though it has a contrasting yellow-green underside. Its wings are very short and the female has a long ovipositor.