"A key part of our strategy is listening to and responding to our customers' needs and developing an agile and flexible network which offers more options during peak periods," said Thompson.
The recovering airline, which is expected to report annual earnings of close to $1 billion next week, is also adding more flights in Jakarta and Singapore.
Christchurch Airport chief commercial officer - aeronautical Justin Watson says the extra flights will help meet the huge Australian demand for the South Island.
The boost over three months would bring an additional 16,128 seats between Christchurch and Brisbane, 12 per cent more seats than the same period last year," he said.
"Last year we had almost 60,000 visitors from Queensland fly into the South Island via Christchurch, which was 5.6 per cent more than the previous year, so there is no doubt the demand is there and growing."
Forecasts suggest the service will bring another 3200 visitors to the South Island, most of them Australians.
"Qantas hasn't flown between Christchurch and Brisbane for ten years, so the return of the service offers travellers competition and choices. Importantly, it also offers a very strong one-stop international connection between Japan and the South Island through Brisbane. We encourage tourism operators to make the most of this connection to ensure this service grows.
"Any way you look at these extra services, they are a massive vote of confidence by Qantas in the market between Queensland, Japan and the South Island and they mean good news for every region in the South Island," he said.
Wellington Airport also welcomed the announcement.
"Competition is exciting for travellers and we expect huge demand for the new Qantas service to Brisbane. It will be the only full service airline on one of our most popular holiday destinations at its busiest time of year," said Steve Sanderson, Wellington Airport chief executive.
Last week Virgin Australia said it would add extra services between Melbourne and Christchurch, and between Brisbane and Auckland, Dunedin, Wellington and Christchurch