The Manila-based ADB said it had also assembled a team of more than 100 experts to prepare a damage and needs assessment report jointly with the World Bank.
Juan Miranda, ADB director general for Central and West Asia Department, announced the package during a trip to Islamabad.
"The extent of human suffering caused by the floods cannot be easily quantified, nor can the damage wrought upon the country's physical and social infrastructure," he said.
"But what is clear is that this disaster is like no other in living memory, and that our response must also be unprecedented, equal to the need, and fast," he added.
More than 1,400 people have been killed, according to Pakistan's National Disaster Management Authority. Up to 20 million have been displaced by the floods which have submerged one-fifth of the country, the United Nations said.
The ADB said it would be leading the damage assessment in the areas of transport and communication, energy, health, water and sanitation, irrigation, social protection and public administration services.
Miranda added the bank was also setting up a special flood reconstruction fund to raise money.
He stressed that it would ensure "that money from donors is used in the right way, at the right time and in a totally transparent manner".
Some potential donors to the aid efforts in Pakistan have been wary of contributing, due to concerns over corruption among officials, and over the possibility of the funds finding their way to fundamentalist groups.
