Charles and Camilla will travel to Cardiff on Friday (September 16), having already attended ceremonies in Belfast and Edinburgh.
Their trip around the UK is part of what is called Operation Spring Tide.
While in the Welsh capital for the accession visit, the royal couple will take part in a service at Llandaff Cathedral alongside senior faith leaders from communities across the city.
They will then head to the Senedd, the Welsh Parliament, to receive a Motion of Condolence.
This will be followed by a reception at Cardiff Castle where First Minister of Wales, Mark Drakeford, and the Speaker of the Senedd, Elin Jones, will get a private audience with the King.
The King and Queen will then meet members of the public who have gathered inside the castle grounds.
Elizabeth II’s state funeral will take place at Westminster Abbey the following Monday (September 19) at 11am, it has been confirmed.
The day of the funeral will be a bank holiday after approval by the King.
On their last trip to Wales in July, the then-Prince of Wales and Duchess of Cornwall spent a week visiting areas and organisations across South Wales including Cardiff, Treorchy, Narberth and Hay-on-Wye.
The Proclamation of the new sovereign will be formally announced in Wales at noon on Sunday at Cardiff Castle.
Prior to the Proclamation, 26 men of the 3rd Battalion the Royal Welsh supported by the Band of the Royal Welsh and accompanied by the regimental mascot, a Welsh billy goat called Shenkin, will march from City Hall at 11.25am along Boulevard de Nantes, North Road and Duke Street to Cardiff Castle.
At the castle, the Wales Herald of Arms Extraordinary, Tom Lloyd, will make the announcement in English and the Lord Lieutenant of South Glamorgan, Morfudd Meredith, will proclaim King Charles in Welsh.
After the readings, members of 104th Regiment of the Royal Artillery will fire a 21-gun salute before the singing of God Save the King and Hen Wlad Fy Nhadau, Wales’ national anthem.
It will be the third time in three days that canon fire has resounded across the city to both mark the Queen’s death and her son Charles’s accession to the throne.
The castle gates will be open from 10am to members of the public wishing to attend the event.
Around 2,000 people will be allowed into the castle grounds on a first come, first served basis.
Charles was formally declared the nation’s new monarch at a ceremony at St James’s Palace, in London, on Saturday.