It will be a big event for both the Duchess and her husband Prince William as they reflect on the eight months that have passed since they became first-time parents.
But how will they spend the new family celebrate the day?
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Spoof photographer Alison Jackson has imagined how Sunday's celebration might look in a special project commissioned by notonthehighstreet.com — and it includes champagne, canapés, and even the Queen taking some selfies, as the royals gather together at the recently refurbished Apartment 1a at Kensington Palace.
One snapshot shows doting Camilla holding Prince George on the sofa, surrounded by Kate, her mum Carole Middleton and the Queen, who is holding her great grandson's hand.
Another picture shows the monarch taking a selfie of the royal gathering, with Prince William making an appearance as the group smile for the camera.
There are also pictures of the Duke and Duchess preparing for the arrival of their relatives. In one, Kate can be seen opening her first Mother's Day card next to her son, who is sat in a high chair, while husband William cooks breakfast in the background.
Another shows the 32-year-old still wearing her pajamas and with rollers in her hair as she plays with her son while William catches up on some sleep on the sofa.
It's not known how the real William and Kate will celebrate Mothering Sunday. But if they do decide to have an evening out, they will have their new nanny Maria Teresa Turrion Borrallo on hand to look after baby George.
The new nanny started working for the royal couple earlier this month, and is set to join the family on their upcoming tour to Australia and New Zealand.
(For more details on Alison Jackson and her work, visit www.alisonjackson.com. More information can also be found at https://twitter.com/alisonjackson and http://www.facebook.com/AlisonJacksonOnline.)