Caldicot Male Voice Choir and Côr y Boro were among Welsh guests invited to attend the first public engagement for the Duke and Duchess of Sussex.
Tuesday's event was part of the Prince of Wales' 70th Birthday Patronage Celebration at Buckingham Palace.
The Royal couple were married in St George's Chapel at Windsor Castle on Saturday.
A team of chefs from Wales were also among the guests.
The Prince of Wales and the Duchess of Cornwall attended the event, which was held in the gardens of Buckingham Palace.
It celebrates the Prince of Wales' patronages and military affiliations as well as charities supported by the Prince.
Caldicot choir's spokesman Lyn Gauntlett said it was a "fantastic experience" for the choir while Mike Williams from London-based Côr y Boro described the event as a "great opportunity".
Mr Gauntlett said: "We are over the moon to be invited to sing at the event, and the icing on the cake really is that the Duke and Duchess of Sussex will be there too.
"We'll be singing a mixture of songs, including around four or five traditional Welsh numbers."
The 45 member Côr y Boro choir will perform "quite a good mix of songs" including Welsh favourites Cwm Rhondda and Calon Lan as well modern songs like Beautiful Day by U2.
"It's an honour to be singing at the event," said Mr Williams, who is the founder and conductor of the choir.
"Being a Welsh choir in London just gives us Welsh expats a home away from home."
Among other guests invited to the celebration are a team of chefs from the Culinary Association of Wales, where the Prince of Wales is patron of the Welsh Culinary Team.
Arwyn Watkins, president of the association, said: "It's a phenomenal feeling to be invited, it feels like a celebration."