Mr Cameron was accompanied by wife Samantha and children Nancy, Elwen and Florence as he left 10 Downing Street for the last time as Prime Minister.
Queen Elizabeth has confirmed Theresa May as Britain's prime minister and invited her to form a new government, after the monarch accepted the resignation Wednesday of David Cameron at Buckingham Palace.
He also stressed his love for Larry the Downing Street cat and exchanged warm wishes and jokes with Labour leader Jeremy Corbyn.
After leaving the Buckingham Palace, May said in a speech, "In David Cameron I follow in the footsteps of a great modern prime minister".
May, 59, has become the second female British prime minister after Margaret Thatcher, who served in office from 1979-90.
She said she wanted to address the poorest and most disadvantaged in society, and the people who had been left behind.
Elected the Conservative Party leader in 2005, Cameron led a coalition government with the Liberal Democrats from 2010 to 2015, and then led his party to a majority in the 2015 general election.
Theresa May took over as Britain's new prime minister yesterday, promising a "bold, new, positive role" for the country less than three weeks after its seismic vote to leave the EU. "As I once said, I was the future, once", he said.He urged his successor, "a brilliant negotiator", to "try to be as close to the European Union as we can be, for the benefits of trade, of co-operation and of security".
Although May backed remaining in the European Union, she has reassured "leave" supporters that "Brexit means Brexit, and we will make a success of it".
"Other than one meeting this afternoon with her majesty the queen, the diary for the rest of the day is remarkably light", he joked.
It's believed that telephone conversations have already been lined up with German leader Angela Merkel and French President Francois Hollande, with whom tough negotiations look certain over the coming months on Britain's European Union exit.
Britain's new prime minister will swiftly begin drawing up her cabinet team and is expected to increase the number of women in government.
Mrs May's husband Philip was standing behind her as she made her first public speech in the role, highlighting the "precious bond" between England, Scotland, Wales and Northern Ireland and between "every one of us".
Britain's Home Secretary Theresa May speaks during her Conservative party leadership campaign at the Institute of Engineering and Technology in Birmingham, Britain on July 11, 2016.
A statement issued by the Palace read: "The Queen received in audience the Right Honourable Theresa May MP this evening and requested her to form a new Administration".
"My only wish is continued success for this great country that I love so very much", he told assembled reporters.