In a statement, Prime Minister Julia Gillard said the funding would be directed through the Red Cross and Red Crescent agencies and non-government organisations, and came in response to the United Nations and the Pakistan government's call for further assistance.
It brings Australia's total commitment to $35 million.
Pakistan's flood disaster continues to worsen, with 20 million people now estimated to have been affected by the floods, and more than 750,000 homes damaged or destroyed.
Despite the international aid effort, new difficulties such as the risk of waterborne disease, dehydration and malnutrition are escalating, due to the lack of safe drinking water, food and shelter.
Ms Gillard said once the current crisis was over, Pakistan would face longer-term challenges like reconstruction and rehabilitation.
"I want to assure the government and people of Pakistan that the Australian government stands ready to assist in these longer term efforts, and to play a role in international conferences that are called to focus attention on the challenge," she said.
"As a matter of courtesy, the foreign minister has advised his opposition counterpart of the government's announcement."
