As she left St James's Palace yesterday and headed to the christening party, she hilariously reminded the waiting photographers, "You're not coming".
But the Queen and Duke of Edinburgh did not attend, with the decision made "some time ago" and not on health grounds, Buckingham Palace said.
Meghan opted for an olive ensemble for Monday's christening of nephew Prince Louis, her first royal baptism since marrying Prince Harry. Take the christening of little brother Prince Louis, where she caught attention for an adorable new hairstyle.
In 2015, his sister Princess Charlotte was christened at St. Mary Magdalene Church in Sandringham, a royal estate near England's eastern coast.
Back at the private party guests were served slices of fruitcake from the Duke and Duchess of Cambridge's eight-tier wedding cake to celebrate yet another wonderful event in the Royal Family's history.
The 11-week-old will be baptised by the Archbishop of Canterbury, the Most Reverend Justin Welby, in the palace's Chapel Royal.
Middleton wore another Alexander McQueen dress for her son's christening. Prince William wore a sharp blue suit and was hand-in-hand with George and Charlotte who wore a white short set and blue and white printed dress respectively.
The list includes Nicholas van Cutsem, former Etonian Harry Aubrey-Fletcher and Lady Laura Meade, who is the wife of royal wedding speech-maker James Meade.
Also present were Prince Louis' six godparents and family members including Prince Charles and the Duchess of Cornwall, Michael and Carole Middleton, and James and Pippa Matthews.
Meghan, Duchess of Sussex, went the Kate Middleton way of things and wore a single colour head to toe.
The Royal Christening Robe was made in 1841 for the christening of Queen Victoria's eldest daughter, and was worn for all subsequent royal christenings up until James, Viscount Severn, who was born in 2007, who was the first to use the replica robe.