Electricity cut out around 9.45am affecting shops and businesses in the centre of town and the nearby industrial area.
The outage left businesses without power and centre city shops having to use cash-only transactions.
Kmart and the Invercargill Central Mall were able to continue as normal, apparently on generator power.
PowerNet said electricity was restored to all customers at about 1.30pm.
The network management company initially said the outage occurred after a power pole went down near the recycling centre at about 9.30am.
However, after further investigation that assessment was corrected this afternoon.
"The outage was caused by a duck flying into power lines – not a downed power pole or lines as previously thought," PowerNet said in a statement.
While PowerNet was able to restore power to the central city area around 10.15am, a further fault occurred affecting other streets which was not fixed until early afternoon.
Invercargill City Council said the city's library was closed this morning because of the outage.
