Joe Jonas was also in high spirits at the Santa Barbara Polo & Racquet Club as he celebrated the prince's win with a special lady by his side: model Karlie Kloss, who is the current face of Oscar de la Renta.
Prior to the game, Jonas, 21, and Kloss, 18, goofed around in a photo booth sponsored by Jack Wills, the British fashion house that designed the jerseys for the match.
In the cute black-and-white photos, the two strike three poses, going from serious to silly – Kloss makes a kissy face! – to romantic. In the last image of their uncensored shoot, they gaze into each other's eyes.
Jonas and Kloss, who has also starred in ad campaigns for Dior and Marc Jacobs, kept close company at the match, which benefitted the American Friends of the Foundation of Prince William and Prince Harry.
After attending the luncheon with the Jacks Wills team and flirting in the photo booth, the two were spotted chatting it up in the stands as they cheered on Team Royal Salute alongside Duchess Catherine and Alex Pettyfer.