Cook Brothers Construction staff moved on to the George St site this week.
One of the major parts of the job will be to raise the roof by about 3m.
Business development director Sam Rofe said a "considerable amount of thought" had gone into the health and safety aspects of the job.
The building firm had submitted a comprehensive plan to the Dunedin City Council to gain a "public-use certificate" that allows the work to go on while the public is in the mall.
He said there were no issues or problems, only "challenges and opportunities".
One of the first steps will be to construct a tent-like structure over the roof to allow the new roof to be built.
Managing director David Bulling said a higher ceiling, and the introduction of natural light, would improve the ambience of the mall.
A link to the Dunedin City Council's Wall Street mall will also be created and, with the existing link to the Meridian mall, the total undercover retail area will be 3ha.
One of the features of the upgraded Golden Centre mall will be a meeting area which manager Simon Eddy said would be promoted as the starting point for the public's "shopping experiences".
He would not say how much the work would cost but considered using a figure of $5 million was "not inappropriate".
Aside from using Auckland architects specialising in mall construction, most of the work was being done by local firms so that "the money we are spending is flowing through the local economy".
The Golden Centre provided space for 20 retail outlets and negotiations were under way to add to that number.
The refurbishment was expected to be finished in November.
One of the longest standing retailers in the centre, Ava Collins, of I Love Paris, said she planned to revamp her store during the next few months, and John Brenssell, of Paper Plus, said his three outlets in the centre were also in line for a major upgrade.
Mr Eddy said a separate project focusing on the food court would be considered next year.
The mall is owned by a group of Otago business people.
