The fun-loving royal, who is a patron of the charity for seriously ill children, attended the event at The Dorchester Hotel on Park Lane.
Prince Harry was given the honour of presenting the award for Most Inspirational Child aged three to six. During the ceremony, the royal had the chance to meet and talk to the nominees of each category and their families.
Speaking to Nikki Christou, nine, from Enfield, North London, the Prince revealed he had just seen baby Prince George at Kensington Palace after travelling back from Essex with Prince William where they had attended the funeral of their close family friend Hugh van Cutsem.
Young Nikki explained to the royal that she shared George's 22 July birthday and that her dad was called George and her brother Alexander – one of the baby's middle names.
"Wow, very, very weird," Harry said. "I've just literally seen him. Normally when I see him he's either sleeping or crying but I've just seen him smile. It was the first time I've seen him smile."
The 28-year-old also took time to speak to little Jonathan He, who was dressed in a tuxedo and dickie bow. Jonathan, six, was the star of the show as he performed a song called I Dig My Garden for Harry, which made Harry raise a big smile.
At the end of the ceremony, Harry delivered a short speech, which he gave confidently and without notes.
He described the award winners as "unbelievably brave" and said: "I'm hugely humbled to be patron of WellChild and I count myself incredibly lucky to be patron, as well as coming down here this evening."
Other celebrity guests such as Penny Lancaster and Tess Daly attended the event.
The fourth-in-line to the throne, who is often praised for his innate ability to connect with children, is heavily involved with fundraising for the charity. Earlier on in the day, Prince Harry attended the BGC Partners' Charity Day where he hit the trading floor and assisted employees with sealing deals over the telephone.
Prince Harry was accompanied by his brother Prince William, but it was Harry who reportedly hit the jackpot by securing a £21billion FOREX trade, a world record trade of its kind.
The revenues from the day's trade went to a number of charities including WellChild and SkillForce, the latter of which Prince William is a patron.