Foreign Affairs Minister Murray McCully said the flooding in the Khyber Pakhtunkhwa region in northwest Pakistan was the worst in living memory.
New Zealand would support international efforts to provide emergency shelter, drinking water, food and medical supplies.
Health organisations were concerned about the risk of a cholera outbreak and it was important aid agencies move quickly, Mr McCully said.
The $2m donated by New Zealand would be shared between the Red Cross, United Nations and non-governmental organisations already in Pakistan.
New flood warnings had been issued and anger reaching boiling point among impoverished survivors complaining they have been abandoned by the government after their livelihoods had been swept away.
