The pair came to Sydney last Monday and the New York Daily News reports they will tie the knot at Cardinal Cerretti Chapel at St. Patrick's Church.
The church overlooks the ocean and the ceremony will be performed by Rev. Paul Coleman.
The Sydney Daily Telegraph said more than 20 women were hired to snip the stems of 150,000 pale pink and white roses that will cover all four walls of the chapel.
Kidman's adopted children with ex-husband Tom Cruise, 11-year-old Connor and 13-year-old Isabella, flew in for the wedding.
Naomi Watts will be a bridesmaid and her sister, Antonia, will be the maid of honor.
Country star Keith Urban held a bachelor party at a yacht club while Kidman and friends camped at a day spa.