The Royal Logistics Corps Bomb Disposal unit was called in by the police and carried out a controlled explosion.
The detonation took place on what appeared to be a building site at around 8.30pm.
A West Midlands Police spokesman said: "We were called to reports of an unexploded World War 2 bomb at a building site on Coseley Road, Bilston, at 3.40pm. A controlled explosion was carried out."
A video was posted by Force Response showing a small explosion taking place.
Force Response tweeted: "It's not just about fighting crime. Ww2 mortar discovered by workman in Bilston. Controlled explosion carried out.
"Controlled explosion on ww2 mortor discovered by workman in Bilston."