The Iron Lady's harshest critics stayed away in a sign of her bitterly disputed legacy. But still both houses were mostly packed, full of lawmakers recalled from their holidays after Thatcher died on Monday aged 87.
"Let this be her epitaph: That she made this country great again," said Cameron, a fellow Conservative.
He said Thatcher was renowned internationally for helping defeat communism during the 1980s and ending the Cold War.
"There are millions of people who know that they owe their freedom, in part, to Margaret Thatcher," Cameron said.
Supporters say Thatcher's free-market reforms made Britain stronger and hail her leadership during the 1982 Falklands War with Argentina.
Messages of support
Critics, though, complain her economic policies and battles with the trade unions destroyed the livelihood of millions of Britons.
Opposition Labour Party leader Ed Miliband sought to bridge that divide by acknowledging her impact on Britain.
"Whatever your view of her, Margaret Thatcher was a unique and towering figure," he told the House of Commons.
Thatcher's son Mark said their family had been "overwhelmed" by messages of support from around the globe, following her death at London's Ritz Hotel after a stroke.
He said his mother would also have been "greatly honoured" by Queen Elizabeth II's decision to attend her funeral next Wednesday, a rare honour from the monarch only previously accorded to wartime prime minister Winston Churchill, who died in 1965.
The service will be held at St Paul's Cathedral in London, where British armed forces personnel from units associated with the Falklands conflict will bear her coffin. A total of 700 military personnel will be involved.
