Guests included children from local schools and representatives of Age UK, Contact the Elderly and Save the Children, as well as young charity fundraisers.
Red, white and blue bunting was hung on the street and live coverage of celebrations elsewhere and replays of key moments from the service were broadcast on a big screen.
David and Samantha Cameron, who attended the wedding in Westminster Abbey and reception at Buckingham Palace, mingled with guests at the street party.
Speaking this afternoon, Mr Cameron said the ceremony had been “incredibly romantic and moving”.
It was beautiful to see two people who really love each other and who are incredibly happy at an amazing ceremony.
It’s a day when we see “the new team”. It was incredibly romantic and moving.
It’s a great moment for Britain, a moment when everyone is celebrating and it’s being watched round the world where people will see lots of things they love about Britain.
The ceremonial, the pageantry, the Royal Family, the institution - but also this beautiful young couple who love each other very much.
Earlier this week, children helped Mrs Cameron bake cakes in the Number 10 kitchen for the Downing Street party, and they returned today to sample their handiwork.
Food and drink was donated or made by Downing Street staff and an ice cream tricycle with umbrella served children treats.