The employees were kept outside the building between 11am and 11.30am, when police judged it was safe for them to return.
“Police have investigated the bomb threat and based on an overall assessment we have not implemented any operational measures,” Torgeir Brenden, the officer who managed the evacuation, told Norway's state broadcaster NRK.
He would not give any details of the nature of the threat.
“All I can say is that we do not see it as specific and therefore no measures were implemented,” he said.
A DNB employee said that many of those evacuated had feared an imminent attack.
“People were the slightly anxious in light of the last week's terror attacks,” one employee told NRK.
The evacuation came as documents handed to a Swedish court confirmed that Moder Mothama Magid, 22, who was arrested in a police raid on the town of Boliden on Thursday night, planned a terror attack on Stockholm.
Last Friday, 129 people were killed in Paris after ISIS supporters unleashed a series of coordinated terror attacks in the city.