The royal brothers and their cousins, Princess Eugenie and Princess Beatrice, gathered for the celebration at the Memphis Hunt and Polo Club.
According to People, the Duke of Cambridge was the life of the party, during the Jimmy Church Band’s rendition of ‘Shout’.
“William had so much fun, he told me he wanted to bring the band to England,” Church told People. “I was surprised with how humble he was, how kind.”
Newly single following his split from Cressida Bonas, Prince Harry was reportedly more low-key than his older brother.
“He was quietly talking to pals, but it was his brother that was really having fun,” Church told People.
However, The Telegraph reported that Prince Harry “twerked” on the dance floor.
A day earlier, the princes spent a day touring Graceland, the former home of Elvis Presley and where the king died on August 16, 1977.