The state government plans to illuminate the landmark at 8pm on Friday with pictures of previous royal visits to Sydney.
King Charles III and Queen Camilla will tour the NSW capital and Canberra after landing on Australian soil on October 18.
Prince Charles and Queen Camilla will visit Sydney and Canberra on their upcoming royal tour. (David Rowland/AAP PHOTOS)
The green light to illuminate the sails comes almost 18 months after Premier Chris Minns dumped plans set by the former coalition state government to light up the venue for the King's coronation.
The cost of $80,000-$100,000 per night was too much for taxpayers to bear, he said at the time.
But Mr Minns on Tuesday said it was important the King was warmly welcomed during his visit to Sydney.
He said the "primary objective" in lighting up the Opera House would be to focus on events taking place in the state capital.
NSW Premier Chris Minns has agreed to light up the Sydney Opera despite the cost to taxpayers. (Dean Lewins/AAP PHOTOS)
Earlier in the week, the premier said he had not changed his view that Australia should become a republic but that would not stop the red carpet being rolled out for the King during his first visit as monarch.
The Opera House sails were illuminated for 23 days in 2012 but that ballooned to more than 70 days in 2022, costing taxpayers up to $7 million annually.
Requests to the government were still increasing and included "trivial matters", the premier said previously.
NSW Labor has rejected a number of requests, since coming to office, to light up the Opera House from various organisations and for religious events.
Friday's display will include a four-minute looping montage of images from previous royal visits.
The King and Queen will leave the country on October 23 to visit Samoa.
It will be the first trip to Australia by a reigning monarch since 2011, when Queen Elizabeth II visited Brisbane, Melbourne, Canberra and Perth.
King Charles visited Australia 16 times before taking the throne in 2022 after the death of his mother.