Everyone within a 300-metre (-yard) radius of the bomb, which was found during terracing work in a residential garden, was required to leave the area.
More than 100 people awaited the all-clear from army bomb disposal experts so they could resume festivities, police said.
The British World War II bomb weighing 108 kilogrammes was found near Ghent's suburban Merelbeke train station, Belgian television reported.
In 1943 and 1944, the area was a frequent target of Allied air raids.