While Ms Gillard flagged the move with Treasurer Wayne Swan, she kept it from most of her front bench until she publicly announced it during a speech in Canberra on Wednesday.
She set the date for Saturday, September 14, but insists campaigning will not start until August.
It has since emerged she told the Australian Greens and independent MPs Rob Oakeshott and Tony Windsor about the announcement ahead of time. But Ms Gillard's cabinet colleagues lined up on Thursday to publicly back Ms Gillard's tactics.
Transport Minister Anthony Albanese insisted the move was normal.
"Never has a prime minister, who's always had the prerogative of calling an election, gone and consulted hundreds of people about election dates," Mr Albanese told ABC radio.
Attorney-General Nicola Roxon also praised Ms Gillard's move.
"I think that's in her nature, to be strong and bold and determined to do things in the best interests of the country," she told ABC radio.
"What I would say is that this is actually a refreshing initiative because it means that we can concentrate on policy," he told Sky News.
Senior frontbencher Simon Crean said Ms Gillard's decision meant political debate would move beyond simply arguing in parliament.
Health Minister Tanya Plibersek told reporters on Thursday she was not concerned the Greens were informed that the date had been set half an hour before the prime minister made her public announcement.
And Mental Health Minister Mark Butler said the early announcement brought certainty to the business community and the wider electorate.
Trade Minister Craig Emerson said he learnt of the prime minister's announcement on his return from India.
Veterans' Affairs Minister Warren Snowdon says announcing the election date so early is good for Australians.
"I think it was a very good political judgment based on what is in the best interests of the Australian community," Mr Snowdon said on Thursday.
He also said he was "absolutely" an advocate of having fixed electoral terms in the future.
Tony Windsor said the prime minister had agreed to consult him and other crossbenchers about the poll date as part of their post-2010 election agreement.
"I was a little bit surprised that she announced it so early," he told ABC television.
Questioned on whether he was surprised the PM had not consulted her own caucus about Wednesday's announcement, Mr Windsor said, "That's none of my business".