Other notable guests there to toast Prince Louis were Prince Charles and Camilla, Kate's parents Carole and Michael Middleton, her sister Pippa and her husband James Matthews, and hot bearded Middleton brother James.
The Archbishop of Canterbury Justin Welby welcomed the royals at the entrance to the chapel.
The godparents included Hannah Carter, a school friend of the Duchess, and Lady Laura Meade, who is married to Prince William's friend and Princess Charlotte's godfather, James.
The little prince was also christened in the Lily Font, a silver gilt font and bowl decorated in lilies, ivy and cherubs.
Following the 40-minute traditional religious service, guests attended a private tea which included slices of christening cake, from a tier taken from the duke and duchess' wedding cake.
The Queen and Prince Philip won't attend the christening.
Prince George and Princess Charlotte each held on to their dad's hands as he guided them towards the chapel.
This isn't the first time the young royal's confident personality has come out after she was caught excitedly skipping at a polo event with her mum, Kate Middleton.
Prince Louis is fifth in line to the throne.
It's days like today that make being a mom so special for Kate Middleton.