Dressed in pyjamas and a dressing gown, George was pictured shaking hands with the President and playing on his rocking horse
But clearly the toddler was especially excited about the prospect of meeting President Obama and his wife Michelle tonight.
The Obamas arrived for an informal dinner at Kensington Palace with the Duke and Duchess of Cambridge and Prince Harry tonight.
But Prince George was also allowed to stay up a few minutes past his bedtime to meet the guests.
Dressed in pyjamas and a dressing gown, George was pictured shaking hands with the President and playing on his rocking horse.
However, one person who was not in attendance was Princess Charlotte. Kensington Palace later confirmed she was fast asleep for the visit.
The rocking horse was a present from the Obamas to mark George's birth, and they also gave him a stuffed toy when Charlotte was born last year.
The rocking horse has the Presidential seal on the saddle and looked to be a big hit with its two-year-old rider.
A Kensington Palace spokesman said: "Prince George stayed up to meet the president and first lady when they arrived at Kensington Palace.
"He was able to show the president and first lady a rocking horse - given to George when he was born - and a stuffed toy - given to George when Princess Charlotte was born - that had been previously given to him by president and Mrs Obama."
The Duke and Duchess of Cambridge and Prince Harry greeted Mr and Mrs Obama in a courtyard at Kensington Palace.
The president shouted "oh there you are - hello" after they stepped out of the presidential black Cadillac, flanked by secret service staff.
William, wearing a blue jacket, trousers and light blue shirt without a tie, apologised to the Obamas, who both sheltered from the rain under a single black umbrella as they made their way towards the door.
"Sorry about the weather," he joked.
Kate, wearing a teal and maroon dress, shook hands with the president and his wife, who was wearing a long camel coat over a lighter camel dress, before Mr Obama offered her the umbrella.
But the Duchess refused it, leaving the US leader to hold it over both his wife and Kate.
The five chatted briefly, laughing together several times, before moving to pose for photos without the umbrella.
Obama earlier steamrollered Boris Johnson on national TV for claiming he resents Winston Churchill because he's "part Kenyan".
The US President blew the London mayor's 'nasty' claims out of the water with the simple words: "I love Winston Churchill. Love the guy".
Mr Johnson prompted uproar today by suggesting Mr Obama removed a bust of Churchill from the Oval Office as a "a symbol of the part-Kenyan President's ancestral dislike of the British Empire".
Furious pro-EU campaigners said the Brexit -backing mayor was plumbing new depths in his Vote Leave campaign.
And David Cameron 's official spokeswoman flatly denied Boris' claims, saying the bust was moved before Obama took office.
Read more: Barack Obama crashes into EU debate as he warns Britain will be 'at the back of the queue'
Tonight's comments came as Mr Obama crashed headlong into the Brexit debate at a crunch press conference with David Cameron .
The US President made a passionate plea for unity as he quoted English poet John Donne's famous words: "No man is an island".
And in a major blow to the Leave campaign, he warned Britain will be left "at the back of the queue" with no US-UK trade deal "any time soon" if voters choose to leave the EU on June 23.
He added: "I think it was a British poet who said no man is an island. Not even an island as beautiful as this. We're stronger together."
The talks and press conference came after the President and First Lady Michelle had a 90th birthday lunch with the Queen at Windsor Castle.
President Obama joked about being driven to the door by the 94-year-old Prince Philip.
He said: "I have never been driven by a Duke of Edinburgh before and I can report it was a very smooth ride.
"As for Her Majesty, the Queen's been a source of inspiration for me like so many people around the world.
"She is truly one of my favourite people and should we be fortunate enough to reach 90, may we be as vibrant as she is.
"She's a real jewel to the world, not just the United Kingdom."