The move makes the US now the only developed nation not to ratify the Kyoto agreement, which sets binding limits on developed countries to curb emissions of greenhouse gases.
Signing up to Kyoto had been one of Rudd's campaign pledges as he led his centre-left Labor party to victory and brought an end to 11 years of conservative rule.
Next week Rudd will lead a delegation to the UN summit in the Indonesian island of Bali where negotiations began on Monday on new pollution targets after the Kyoto pact expires in 2012.
"Australia's official declaration today that we will become a member of the Kyoto Protocol is a significant step forward in our country's efforts to fight climate change domestically - and with the international community," Rudd said.
Rudd's predecessor, John Howard, had argued that Australia would not agree to a pact setting greenhouse gas emission targets unless big polluters among developing countries such as China and India were also subject to binding targets.
Australia's change of course is likely to see the country's standing soar at the Bali climate talks, adding to pressure on the US to join the Kyoto framework.
After taking the oath of office at Government House in Canberra, Rudd gathered his cabinet for their first formal meeting saying Australia was turning "a new page into the future".
|Rudd's cabinet includes the first woman deputy PM and the first climate change minister [AFP]|
"It's getting down to work on the agenda we put to the people during the election period. I'm really looking forward to that," he said.
Aside from reversing Howard's refusal to ratify the Kyoto pact, Rudd has promised several other sharp changes in policy from his predecessor, including pledges to pull all Australian troops out of Iraq and dismantle union-busting labour laws.
Included in Rudd's new cabinet are Julia Gillard, Australia's first woman to hold the post of deputy prime minister, and Penny Wong the country's first climate change minister and first Asian-born minister in the Australian government.