Prince William and Catherine visited the Barclays Center in Brooklyn to watch a basketball game between the Cleveland Cavaliers and Brooklyn Nets, and met up for a chat with the two pop stars between the third and fourth quarters of the game.
The music couple and royal couple were seen laughing and joking during their short get-together and were believed to have discussed the Brits' trip to New York as well as wishing each other well for the festive season.
An insider told People.com: ''Jay Z wished Will and Kate 'Merry Christmas' when he was talking to them.''
The loved-up couple - who are expecting their second baby in 2015, a sibling for Prince George - dressed casually for the game, with Catherine wrapping up in a grey Tory Burch coat and skinny jeans, while Prince William sported a blue and red plaid shirt.
Another onlooker described the moment Beyonce, 33, and Jay Z, 45, met the couple as a ''mob scene''.
The source told E! News: ''Bey and Jay got up out of their seats during the break before the fourth quarter and walked across the court to say hi.
''Everyone was standing up and gawking. It's a mob scene around them.''
William and Catherine - previously known as Kate Middleton - also met with basketball professional player LeBron 'King' James who later gushed about the meeting on his Instagram account.
Along with a picture of them chatting, he wrote: ''This very moment will be forever remembered and put up in my house. It's all good and all smiles on this side.''
Captioning a second image, he continued: ''Wow what an Honor! This game has brought me so much and I'll never take it for granted! The King, ''Duke & Duchess. (sic)''
The sports game is one of many events which the couple are visiting during their three day trip to the Big Apple, while Beyonce and Jay Z are busy trying to secure a deal on an estate in Beverly Hills worth $85 million.
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