Camilla, wearing a light blue dress and a dramatic feather fascinator, smiled with Prince Charles as Europe's youngest monarch made his solemn declaration to the Dutch throne at Nieuwe Kerk, a 15th century church next to the Royal Palace on Dam Square.
Joining Charles and Camilla were Denmark's Prince Frederik and his glamorous wife Princess Mary, Prince Haakon and Princess Mette-Marit from neighbouring Norway and Prince Daniel and Princess Victoria of Sweden.
Princess Mathilde and Prince Philippe of Belgium also attended and Spain was represented by Prince Felipe and Princess Letizia.
Prince Albert of Monaco was another VIP guest at the festivities, the largest gathering of royals since the Queen's Diamond Jubilee last year. Royal invitees from further afield included Japan's Prince Naruhito and his wife Princess Masako, making her first official overseas appearance in 11 years.
Secretary General for the UN, Kofi Annan and his wife Nane Lagergren also turned out to show their support as did representatives from the European Union, José Manuel Barroso and Herman Van Rompuy.
Princess Amalia, Princess Alexia and Princess Ariane headed members of the Dutch royals, including Princess Beatrix. Seated at the front in their matching blue outfits, the 'Triple A' princesses and their grandmother proudly faced Willem-Alexander and Maxima.
Following the rest of his family were King Willem-Alexander, Queen Maxima and the main cortege, who proceeded to the church for the investiture ceremony.
Willem-Alexander, 46, and Maxima, 41, then took their seats in the church where their religious wedding ceremony took place on February 2, 2002, facing the royal symbols: the crown, the scepter, the orb, the sword and the banner with the Dutch flag, along with a copy of the constitution.
The hour-long oath and investiture ceremony began with a rousing rendition of the national anthem to welcome the new King and Queen in the church before King Willem-Alexander then made his first speech as King of the Netherlands.
Rapturous applause spreads through the church as Willem-Alexander finished his speech and a musical tribute to Princess Beatrix began. The Amsterdam Children's Choir then performed a song by famed Dutch musician Herman van Veen, specifically composed for the special day.
Willem-Alexander then remained standing as members of the two chambers and representatives of Aruba, Curacao and St. Maarten swore their allegiance to the new King and Head of State.
Trumpets sounded as ceremony drew to a close and the guardsmen in Dam Square reformed to welcome the new King and Queen.