Princess Charlotte's Christening on 5 July will be the first time the Cambridges will appear in public as a family of four.
The Duke and Duchess of Cambridge, Prince George and baby Charlotte, who was born at the start of May, have yet to be seen all together.
Guests including the Queen, the Duke of Edinburgh, the Prince of Wales and the Duchess of Cornwall, Kate's parents Carole and Michael Middleton, other family and Charlotte's godparents - who are still to be announced - will gather at the Church of St Mary Magdalene in Sandringham - close to the Cambridges's Norfolk country mansion Anmer Hall on 5 July for the traditional ceremony.
Much like the Christmas Day service, members of the public will be allowed to gather nearby to see Charlotte and the royals as they make their way to and from the church.
A Kensington Palace spokesman said William and Kate were "delighted" that the paddock outside the church would be open to well-wishers, and were "hugely grateful" for people's warm wishes since the birth of their daughter.
"While the service inside the church will be private, The Duke and Duchess of Cambridge will be pleased to welcome well-wishers into the paddock outside the church," the spokesman said.
"The Duke and Duchess are hugely grateful for the warm wishes they have received since Princess Charlotte's birth - many of them from local people in Norfolk - and are delighted the paddock can be opened on the day of the christening."
Charlotte's uncle, Prince Harry, will miss the event, having already left to spend three months in Africa where he is working as a ranger following his departure from the Army.
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Although the baptism will be a private affair, the star guest is likely to make a rare appearance for the cameras - only the second glimpse of the Princess in public since she was born.
William and Kate are set to bring toddler George, who turns two at the end of July.
The Archbishop of Canterbury, the Most Rev Justin Welby, will conduct the ceremony and give an address. He will be supported by The Reverend Canon Jonathan Riviere, the Rector of the Sandringham group of parishes.
For George's christening in October 2013 at the Chapel Royal, there was a guest list of just over 20 people and a number of senior royals were missing - including the Princess Royal, the Duke of York and the Earl of Wessex, but the tiny congregation did span four generations of the Royal Family.
One historic image released to the media showed the Queen with three future monarchs - Charles, William and George.
Princess Charlotte Elizabeth Diana of Cambridge, who is fourth in line to the throne, was born on May 2 at 8.34am, weighing 8lbs 3oz.
Kate and William proudly showed their sleeping baby princess, who was wrapped in a shawl and a bonnet, to the world as they left the Lindo Wing of St Mary's Hospital, London, just hours later on the same day.
George had been to visit his new sibling earlier, but was taken home separately while his parents stayed with his sister.