The Tuggeranong Hyperdome reopened about 1pm on Sunday, the shopping centre said on Facebook, citing unexpecteded delays in building works.
The centre announced plans to open late on Sunday while "significant" upgrade works took place. It had earlier expected the works to be completed about 10am.
"To ensure the safety and well being of our retailers and customers, the centre will be closed until the work is completed," the centre said on Facebook.
The ACT government warned sections of Athllon Drive, Reed Street and Scollay Street would be temporarily closed from 6am to 10am to allow for the works to take place.
On Sunday morning, visitors to the centre reported seeing a helicopter deliver goods, understood to be an airconditioning unit, to the roof of the shopping centre.
But 10am came and went, prompting digruntled shoppers, movie goers and retail staff to vent on the shopping centre's Facebook page.
"Not happy the streets outside are chaos," wrote one.
"Thanks for updating us finally. When we’re home. After waiting. For hours," said another.
Others, though, labelled it a "first world problem".
Just before 1pm, the centre posted an update saying the centre was open.
"UPDATE: the works have now been completed and the centre is now open."